1) For the town hall quests: everyone gets the quest if you're in the party. For the guild hall quests: each individual character must get the quest, and must receive credit for it individually (you do this by switching the active character in the guildhall). Annoying, but workable.
2) Assuming that you don't want to exploit the "Inn Gold Bug" feature of the unpatched version, a good way to raise money is to buy arrows and sell them back. They sell back for more than you bought them, so by buying and selling them, over and over, you can raise a bit of money.
3) Unless you have been specifically dispatched to bring back a gem or artifact from a quest, you can sell all the gems you find. Unfortunately, they probably won't bring much money...but every little bit helps.
4) Save money by not ID'ing items...most of the stuff you find around Valeia isn't worth ID'ing. Use your hard-earned money to buy guild membership and training for your forces instead. Eventually, you'll be able to learn the Ancient Lore trait, and then start studying the Artifacts skill, through one of your guilds.
Hope this helps!
-Sazerac