Take a look at this:
http://forums.d2jsp.org/topic.php?t=61995986&f=174It's a bit outdated, but still has quite a bit of vital info.
Basically once you are 20 you teleport to godlands (an area that has black ground and lava fissures, usually in the center of the map, with a bunch of lvl 20 players) and farm for better gear and stat potions. I would save those potions and use them to max once you are more comfortable with the game.