Best class for farming - wizzard, or archer w/a dbow . If you are a noob then necros are almost as good as wizzards and can heal.
If you are maxed ( 4/8 ) you can solo abyses since they drop vit and def. Udls and sprite worlds are pretty easy . All dungeons have a 100% pot drop rate if you are soling them. Also try doing castles and oryxes as much as you can, since O1 and O2 can drop upto 3 pots at once.
Also if you got mad skillz try farming events with a rogue. You will be hauling ass in no time. ( not IRL )