I probably liked the earlier parts with Jellal's arcs the most, including the one where Wendy was introduced. I reckon it's because I liked both Erza and Jellal (and Wendy), and the setting also fit my tastes: A man and woman pushed to the opposing sites but still liking the other. It's too bad Jellal never was put to much use later in the manga, but on the other hand there were a lot of characters, so perhaps it makes sense most were treated somewhat superficially and only the core MCs went through everything.

The tournament arc with the gate and dragons wasn't bad either, mainly due to the dragons themselves.