Fire mage is by far the best moneymaker,
go for PaperMage (fire), u'll have high damage even with cheap items.
when u have AOE-skills, u'll start making fast gold.
first, with the gold u collect, go buy paper (lvl1items) items for your char,
buy upgrade scrolls. and try to make a +8 paper set. Add mp (+15 at upgrade 8) and u'll have BOSS damage.
Dont even think about farming bosses... The servers are FULL, and 75% cheats/hacks anyway. They will be there before u can say out the alphabet.
And a mage isnt a very good solo Boss farmer.
anyways,
i recommend you to buy Knight Cash, and buy scrolls and sell them for ingame gold.
use the gold wisely, and u'll have a powerchar with little money spent.