Which episodes of Konjiki no Gash Bell are essential? The anime series of Konjiki no Gash Bell has 150 episodes. I watched up to episode 26. As far as I saw, in most of the episodes, the main plot does not advance. Watching all those 150 episodes will be very time-consuming if that's going to be the case for the rest of the series.

Please give me a list of the essential episodes so that I could skip over the non-essential ones.
According to this page, there are 121 canon episodes.

Filler episodes for Zatch Bell/Gash bell:

31-35
89-100
139-150

Once you reach the end of episode 138, read volume 22, chapter 212 to continue the story properly.
139-150 have parts in them that are canon, but they are not completely canon, they are mostly filler and the manga is better.