Just wondering if anyone has dealt with this...
To realize a higher confidence level, does one spend confidence to buy the next level? For example, have 5 confidence, if you spend them all at once, do you spend 10 confidence points all at once, essentially to move confidence to from 1 to 2? Same for a confidence score of 3, spend 15, when at 2, and you get to 3? How does one handle increasing confidence scores? When treated as ability one can spend as many confidence points as the ability score at any one time. Just trying to get a handle on the mechanics of increasing the Confidence score...
That's an interesting question, but I'm not sure advancing it as an Ability would be best. For one thing, it starts at 1/3, and then is raised to 2/5...
In your example, the character would not be able to spend all 5 Confidence Points at once since his Confidence Level is 2 - the maximum number of points he can spend at once.
I'd just arbitrarily decide, with the help of the troupe, when a character is ready to have his or her Confidence Level increased, but I don't know that I would connect it at all to the amount of Confidence Points owned at the time, but rather on the story elements that led to the increase in the first place.
As an SG, I dislike the arbitrary...
I like setting guidelines and then allowing players to realize those guidelines as they see fit. Ability scores are the closest measure I have of this particular "Ability." It's certainly closer to an Ability than an Art. And it makes some sense when you look at it from a Tytlus perspective, since they have this virtue by default, that they are Self Confident and start with a 2 (5) Confidence "Score." They are effectively 10 more points away from realizing a score of 3, of course they can spend them on other things, as they might be inclined... as the saga advances... Of course, someone with a score of 3 (0) is also unable to spend confidence, so....
As you suggest, it's an interesting question, but I have a tendency to dislike SG fiat for handling these things. And Confidence seems to be an ability as it is represented under the RAW. You can spend up to the ability score... So how does one advance the Ability score is the next question...
I understand and respect where you're coming from; it's just not how we usually handle things.
That being said, another reason I dislike the system is that is "prevents" people from spending Confidence Points, which seems counterintuitive to me.
Well, as you say it prevents people from spending confidence, let me suggest that it forces hard choices. 
Spend confidence... by all means. It just means that you delay your capability for expending confidence at a later point.
I'm interested in the extremes. Someone who is interested is getting his Confidence to 3 is interested in getting to a Confidence of 2 (18), at a minimum. When he progresses to 3, he spends 15 confidence points, leaving him with 3 unspent Confidence points to exploit at his next opportunity... So he is at 3 (3). Truthfully, I see very few characters progressing beyond a Confidence score of 3... A Confidence score of 4 is just frightening. Someone who can change a die roll of +12 is just scary... Even +9 is pretty scary. I just have a character in Bibracte who is reasonably close, as I envision it, to progressing to Confidence 3...
You could ask though, what ability there is in Ars that it requires 15 years of work just to gain enough "confidence experience" to raise the level to 2? The Tytalus apprentice struggles against great odds for over a decade and after all that time only gains a second point of Confidence.
As the book suggest a person can reasonably expect to gain two or three Confidence points per session. In just one story alone spanning a week or two of story time, a person could if they played say ten sessions, have enough "confidence/XP" to have a 3 in confidence. So you can see thinking of the Confidence trait as a ability is impossibly unrealistic.
More than another other trait, Confidence is most alike True Faith. Would you allow your fellow players to raise their True Faith like they would an ability? Do such and such amount of prayer, good works, ect. and you get bumped to True Faith 2 after what a year of game time?
Confidence is not simply arbitrary, but is rather a discussion among the players to determine if one of their fellow players has demonstrated such stalwart will and self-determination and belief in one's own abilities, that they have earned the right to be one of the most self-confident and determined being on the planet! To raise Confidence from a 2 to a 3 is a true heroic feat.
Look at the other beings of a level 3 Confidence, given as example by Ars, a Might 50 dragon that lived for centuries if not millennia, a Angel with a Divine might of 50 which few playing magi would be capable of withstanding. Even the examples of devils and magical titans and faerie lords only attain a Confidence of 2.
Confidence is supposed to flow and ebb within the player's character. When a person's confidence is low, they feel as though they can never overcome problems, but when they have say 20 points of confidence, then for an entire day if they choose they can simply accomplish every feat nearly by will alone. IMO Confidence score cannot be so easily bought by simply saving up your will, if anything that defeats the purpose of will of the self.
If you must score it then do so by saying every time a character successfully accomplishes a goal that required their full attention for an entire season of playing, then they gained ONE XP of confidence. But they had to accomplish this on their own without even the hint of help from those around them. Then sure give them one xp of confidence.
Advancing Confidence Score never really came up in my sagas, but I always had this in my back pocket.
If a player/character wanted to increase a Confidence Score, it would be done as the result of achieving a difficult character goal. If the humble watchman finally becomes Turb Captain, that sounds like a Confidence boost. Has the magus made his research breakthrough? That could be a Confidence boost. They're not arbitrary, being closely tied to the character's goals, but it's not a purely mechanistic process, which I think would actually work against what Confidence is.
I think the above helps to guide players too. It gives them additional incentive to work towards some end that is and should be important to the character.
That's why there is a huge difference between Confidence Score and Confidence Points. Points come and go, if you remember them mind you. The first years we forgot to award them, and the noobs did not understand the system and never spent them, the veterans were loath to spend them because they felt they would not be replenished. Once we remembered dishing them out we also started spending.
So, points come and go, but the Score is hard to change. The Score is how much difference your belief in your self can do. The Tytali struggling a decade and a half against all odds and gain a Score of 2. Sure, they also get 2 more Points, but those are peanuts!
We've neve even considered how to raise the Score or that there could be a Score beyond 2.
But as Stories are the highest currence this should be the result of a series of stories all coming together for a final goal. I'm not keen on a mechanic for saving up exp or anything like that.
(Edit) BTW I think a Score above 2 is beginning to be very unbalanced. Sure you spend a lot of your Points each time you get this whopping bonus, but if you save up you can really cause trouble.
This.
I seem to recall having read published NPCs with a confidence score above 2, but the only example I could find was Phillippus Niger, Arch Magus of House Flambeau and undisputed master of Perdo Magics (according to his discription GotF, p. 59-60), who has a Confidence score of 3(5).
which coincidentially should give you an idea of what it takes to have confidence score 3 I think.
I should perhaps also note that the Goetic power of Ablating (RoP: tI, p. 115ff) allows confidence to be bought up like an ability, though that appears to be a characteristic of Ablating itself.
I really like this mechanic. Is there anything hinting at it in the books or did you come up with it yourself? Might implement it as a houserule.
By RAW, no.
Vespasian had an interesting reference though.
Let's look at the Tytalus, and treat Confidence as an ability...
Standard character as a Confidence score of 1, and 3 points, to spend. That's 8 xp.
The newly gauntleted Tytalus has a score of 2, and 5 points to spend. That's 20 xp. The difference is 12 xp. If we assume that the Tytalus earns 1 confidence point per annum for his apprenticeship, on average, he'd acquire 15 xp for Confidence. He would spend 10 to raise the Confidence score from 1 to 2, leaving him with 8 xp remaining. Let's assume that his gauntlet required him to use confidence, and he tried, but was only able to use 1 point, initally, but the expenditure wasn't enough to win the contest against his master decisively. That expenditure transformed him, though, and he spent 10 xp on the spot to advance to a score of 2 Confidence, with 7 points remaining, two of which he used at a key point to defeat his Master in the gauntlet.
Or something...
I think I'm going to stick with the accumulate xp, and spend them to acquire a higher confidence score, but one can only do so when the story of the character calls for it, either because it's necessary to win, or because they have realized some major goal...
You can create a character with a Confidence of 3 from the start. Take the Self Confident Virtue, and if eligible, take the Heroic Personality Flaw.
I think raising Confidence (from 1 to 2, or fron 2 to 3, etcetera) should be a troupe decision. Meaning, if the troupe and SG thinks you are eligible for an increase, them and only then, you can contribute XPO to increase the score by one.
What would make you eliigible? Succeeding and increadibly awesome actions that require spending Confidence (examples: making a ship fly with a spont spell planning to spend confidence and rolling a 1, placing in the top three in a contest versus magi much older than you, mythic heroic actions and the like).
So a player cannot plan on it. They become eligible after doing lots of stuff, the SG & troupe tells them when, and they spend the xp after.
Best of both worlds 
I had thought about this but it doesn't work. Both raise confidence to 2. Applying both leaves it at 2.
I feel like I read a character with the Self Confident Virtue taken twice. I know that's now how it reads, but I get the feeling I read it.
Anyway, if you want a huge Confidence Score, go hunting demons and using Ablating. Then you can be extremely confident your soul is headed to hell. 
Chris
Ovarwa not only beat me to it, he was also marked less sarcastic about it 
+1 point for Ovarwa
Lazy playtesters! (well, I don't remember to check every virtue of every NPC, sorry!)
That is indeed the one RAW solution I could find too.
Well, I think I'm fine with just allowing the character to spend confidence like XP to raise the score, as if it were an ability, with a few other stipulations. There has to be some troupe agreement that the character deserves to raise their Confidence score. The character must have used confidence to the maximum amount possible at the level of the ability score. The character must have enough confidence to buy the next ability score + having enough to expend to the full extent possible with the new confidence score. Finally, confidence is only raised when a situation calls for it, when the character can rise to the occasion and needs the full bonus the new score in Confidence would make possible. And this isn't a cheesy roll, the result must be necessary and have an impact on the story...
To raise to 2, one needs 12 Confidence points 10 for going to 1 to 2, and 2 more points to spend immediately. They must have used confidence one time previously, as well.
To raise to 3, one needs 18 Confidence points, and must have spent at least 4 confidence by using two confidence points on a roll on two different occasions.
To raise to 4, one needs 24 confidence points, and must have spent at least 9 confidence points as above. Probably not going to get to this level very often, but man...
It's not cheap, it requires the character conserve confidence, knowing when to hold 'em and knowing when to fold 'em. As the character becomes eligible for the increased Confidence score in total confidence points available, can break out the discussion on whether the character is eligible for story reasons, and if the troupe agrees, the next opportunity where spending the next level of Confidence is required...done.
There's a lot of stuff about increasing Confidence in Realms of Power: The Infernal...
There is - but aside from Ablating, I could only find the stuff on getting more Confidence points - do you have the pages for the ways increase score?
Another canonical example of Confidence score increase is from A&A -- an artist who achieves an artistic reputation score of 8 is awarded a 1 point increase in his Confidence score. Again, this is something that may take literally decades to accomplish.