I'm a neophyte that just got the 5e Core Rulebook and was interested on trying to play Solo, to learn the system! (Also because I'd probably not be able to convince my friends to play a game this crunchy within the next decade or so).
Currently I'm using the Jerbiton Magi preset (pg. 26) with a few changes and a Knight companion, since my magi can't really do much damage from the get-go (nor he intends to anyway).
As for the Covenant, I'm planning to make a Winter ruins Covenant preset (pg. 70), but given I'm playing a single magi (and one just out of the gauntlet at that) I'd assume there must be other Magi in the covenant, at least their Parens, right? How many Magi should there be in a winter covenant, and are they usually fully stated out?
As for the Covenant resources, is it wise to spend the 200 starting BP in Vis? or are there better uses for a fledgling magi?
Also, how many Grogs are recommended for a magi? Should I create a small group (3-5) of them?
Thanks in advance, and sorry for the torrent of questions!
Not necessarily. He might have been invited to help the old, ineffective remaining mages. Maybe because they are facing some issues that only a Gentle Gifted mage can overcome ?
Or because he ingratiated and was invited as a favor - one of the remaining mage suffers from a strange curse (possibly a bad Twilight episode) that can only be soothed my music (between Free Expression and Puissant Music, it will play right in the Jerbiton's hand).
Another alternative, one of the remaining mage is one of the last representative of a school of singing mage, a bard of sort and is looking for a heir, both to inherit the covenant, but also his legacy and duty as master bard.
Depending if you have some additional book like Tribunal (Normandy or Hibernia for example), House (Societas in your case) or The Mysteries, you can build on it and draw some inspiration as a goal to achieve within 15-25 years.
Don't fully stats the remaining mages, old mages are tedious to fully develop, unless you want some practice exercise. However having a few lines describing their house, specialties or pet topics can be useful, as well as how quirky they became with age (how close to final Twilight, Decrepitude or insanity are they?).
Although vis is useful, I would suggest you think more on what kind of adventures your mage wants to take part and what he does not want to do.
Take boon to avoid the task/adventure he does not want to do (if he does not want to hunt for vis, then yes, having a large collection of vis is nice, but are the remaining mages - who need powerful longevity potion - going to let him free access to the vis store ?) and take hooks for those he would like to have.
It will naturally prompt adventures towards what you are looking forwards and remove or alleviate the part you will find annoying for your mage.
And a useful link where you can find a ruleset for soloplay. This ruleset has been fully tested and even if I am still tweaking it, it works well for the first 20-30 years if you start straight out of apprenticeship.
If you use this ruleset, I would suggest to build your covenant as a Spring covenant within the frame of a Winter covenant. Let me explain: as the youngest magus, you do not have access to the full resources of the covenant, thus, the mage has access to resource more akin to a Spring covenant, but as he earns favors and make himself useful or even indispensable to the older magus, he slowly gets more access to more resources, or discover that they have not been well managed and have been squandered by decades of neglect and carelessness: rotten tomes of once-excellent Summae, slow plundering of silver coffers, etc...
So when your mage earn rewards, instead of coming from outside spoils of victory, he is getting clue to where was stored a pile of labtext and tractatus, or a mage remembered that he had been using a tome to level his uneven lectern, etc.
Your mage can spend half his adventures trying to run a dilapidated covenant to make it functional enough to attract other mages and the other half scavenging and retrieving lost knowledge from sanctum of long dead mages, but with fully functional defenses, live traps and even a ghost or two. A winter covenant can become a target from competing covenant - so politics to secure alliance and protection would be needed - but also from marauders led by edge wizard keen to plunder resources or even claim the site for themself if they believe the defenses have crumbled.
One way you might take it is to say that there is only one elderly magus there, who finally managed to leave his lab long enough to realise the other magi had passed into Twilight, died, or left, and decided to invite some new blood into the covenant (perhaps the apprentice of an apprentice of an apprentice!). Being so ancient and Twilight-scarred, they provide some fun rp opportunities but won't unbalance your game (or create too much work) because it's unlikely they will want to go adventuring. The covenant itself would hold all sorts of secrets your characters can explore, without too much interference from the occupants.
It is not really possible to answer your questions without knowing a lot more about what you want from your solo game.
Do you spend all your BP on vis?
if you want to play the system, and you assume a smooth Order-wide market (using e.g. the price list from the Andorra saga), then yes
it probably is not very plausible that your covenant has insane amounts of vis and no books
but, the BP costs are ill aligned with in-game vis costs, giving that room to play the system
OTOH, maybe the market is not as smooth as some players assume
how many grogs?
a travelling magus will almost always have that entourage of 3-5, including shield grogs, servant, animal handler, and someone who can negotiate with mundane traders without the penalty of the Gift.
but do you want to play 3-5 grogs?
maybe the grogs are theres, but only as specialists and not fully designed grogs
you should make the grogs you want to play, and avoid biting off more than you can chew
how many specialists?
covenfolk is a means to wealth, and particularly large library crews are popular with players
I do not find unbounded crews to be very possible, and particularly Winter covenants have entered WInter by being dysfunctional, often failing to retain their crews
large crews means bookkeeping, so if you do not enjoy bookkeeping, keep it small
is the magus alone in the covenant?
the story of aging magi recruiting a young one to their Winter covenant and then all entering final twilight is common enough, so if you want a singleton covenant, that works
realistically, a singleton covenant should find it hard to survive, but you tell the story you want
a half-senile magus close to final twilight is not going to add that much to your survival chance anyway