@callen; I believe no "astrological virtue" can affect a seasonal activity, since it's active only part of the season. But I think that's a bit off topic.
I totally agree with whomever suggested Self-Confident as a Virtue.
A good reputation (including one earned in play) should also not be discounted!
In general, it seems that there's a lot to be gained for specializing the silver-tongue mundane: either for use in certain times (with astrological virtues... but I think that's not really worth it) for use "against" certain targets (Venus Blessing, Alluring to ) or for specific uses. Ultimately, I find the latter the most interesting. As Ezechiel first and callen later pointed out, if you want to be "well-rounded" in social interaction, you need a high score in Bargain, Charm, Folk ken, Leadership, Guile; plus possibly Intrigue, Etiquette, Artes Liberales (for rethoric). But many of these abilities are different means to the same end, even though some might be more effective than others in certain circumstances, in the same way that different weapon skills are different means to the same end. You can convince a merchant to barter a horse for your sheep by driving a really hard Bargain; by spinning some incredible story about the value of the sheep (or maybe about some illness having taken the horse...) with your Guile; by seducing him with your Charm; etc.
Is it worth investing in half a dozen abilities, or is it better to focus only on one or two, accepting that they'll be less than ideal in a few situations (and of course, having basic skills in the others)? The latter seems a better solution, not only because you can then focus your xp, but because you can focus your Virtues: Affinity, Puissant, and the oft forgotten Learn from Mistakes (as well as Cautious, of course). And which skills would you choose to complement each other?
One thing to keep in mind is that the rules for debate revolve around three "attack" skills (Folk Ken, Intrigue, and Artes Liberales) and three "defense" skills (Charm, Guile, and Leadership). If one is engaging often in debate, it might be worth to invest in one attack skill and one defense skill, accepting that the adversary might gain a +3 bonus to his attacks (and impose a -3 penalty to yours) by choosing the correct response. Folk Ken + Guile seems a solid combination that will almost always net you a +1 bonus to your Guile roll. Intrigue is also useful in many many contexts, and if one goes that way, Charm has less potential to backfire than Guile. Leadership seems more restricted, since it generally acts only on those you have (or are trying to assert) authority on. Artes Liberales is useful for the magus (and the Astrologer!) but much less so for the "general" social character.