The main thing that I never got in the beginning was slingshotting up the levels. At level 1 you should be killing level 2s, at level 2 level 3s (preferably level 4s) etc. Is there a specific dungeon you are having trouble with? Some bosses are very hard with the wrong strategy (caster vs melee). What are you prepping too? Stuff like that.
Maybe do a playthrough and post it over here ( viewtopic.php?f=3&t=1974
) so we can give you some advice.