I would definitely start a guild first thing, I've recently started to save up for one... though 21s isn't much... ^_^;;
I'd also give one gem to the three characters I play, and maybe one to the one I don't(that I still have for some strange reason. O.o).
Then with the remaining 5/6 Gems, 900g, and 800s, I would Put 4g in the bank, use as much money as I need to buy +9's for myself (which probably wouldn't even cost 2g), and then I would ask anyone in my guild/all my friends if they needed money for anything, then give them 100s, even if they didn't need anything. ^_^
I'd definitely give at least 500g to the guild itself, so we can host more fun events and do other awesome stuff.
And last but not least, I would buy all the T2/T3 potions I need, a stack of each of the T3 buff scrolls, and five stacks each of both Elderine and Uruga scrolls.
I hope that I would be able to make all my friends happy.