THere are no items you will need to take from one act to another. All the quests are act specific <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
I normally only take the stuff i really like to the next act and sell the rest in the battlefields.
The only things i would make sure i have from act 1, is (as Raze said) the summoning doll, and the book, teaching you beginner ranaar language (page 40 of the strategy guide). All the rest of the items becomes mere trade items to me <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
