once you have your yellow, make sure to fort it to at least +5-7 (you don't want to break it if you can't afford mallets yet). If it has slots, stone it with +8% magic crit damage. Grind your masteries up as well as gear cultivation. I suggest INT + M-ATK on the staff.
Get a 71+ sprite and try crafting the set yourself, or if you hate crafting (as I do) then you can save up money and purchase it from another player..
I don't have much advice for being an AM, but the others answered that quite well. Just fort your staff so you can kill things faster, and work on saving up money.
Edit: Oh, and one other thing.. don't care what others think
Just do what you want to do and have fun.