If you're a healer, you can expect to get party invites for abyssea as early as when you get Cure 4. Even more of them if you're a whm when you get Cure 5.

As a melee, you can't do much until you're above level 70. For levels 10-50, i have usually duoed with friends for 20k-ish exp/hour, but that method slows down considerably as you get close to 50, and isn't too fast between 50 and 70 at all. Between those levels, i have resorted to level syncing to lower levels because I think keywhoring is really boring.