theres 2 leveling coins that u can buy.
level 25, from Mina and level 50, from Arturo. (so they level u up instantly to 25/50)
collect EXP Coupons from drops and quests (mushking)
audish (in henesys) should give u enough missions to help u level.
exchange-shops are useful to get EXP by exchanging drops.
so, instead of selling the drops from monsters, exchange them.
find good kill places. theres many maps with lots of spawn that are easy to kill. (1-shot-kill)