These are places you can lvl up easy and get loads of expierence:
Where 1-10 Stony Field to Tamoe Highland 11-16 Outer Cloister to Catacombs 15-20 Sewers 19-24 Lost City to Tal Rasha's Tomb 22-25 Anywhere in Act 3 24-28 Outer Steppes to Plains of Dispair 26-34 City of the Damned to River of Flame 32-36 Act 5 37-50 Act 2, Skip Act 1 but go for Quests 50-60 Act 4, Might want to skip Act 3 60-65 Act 5 65-70 Act 2, Skip Act 1 but go for Quests 70-80 Act 4, Might want to skip Act 3 75+ Act 5