The first (and the best, in my opinion) Dragon Ball series.
Very underrated to this very day , being often overlooked in order to focus only in the events from Dragon Ball Z...But honestly, skipping the original Dragon Ball as a whole, if anything lessens all the enjoyement the sequel series could have.
If I have started watching Dragon Ball Z without having seen Dragon Ball first (Like many fans from the United States did) I would have been completely lost, completely unable to follow the story and the way the characters interact.
In Dragon Ball we are able to witness the very beginning of Goku's journey and how he meet his friends, and the way he kept improving himself as a fighter. The emotional impact of the deaths of some characters in the first arc of Dragon Ball Z is largely connected with the original series.
Piccolo's transition from villain to hero is not as good without having the chance of seeing how he firstly appeared in the series as the main antagonist. (And honestly, is the most convincing redemption arc from Dragon Ball, along with the change of heart Tenshinhan had)
Some people dismiss the series simply because of its whimsical nature, focusing mostly in the "serious" parts (Like the Frieza and Cell saga), but being fun and whimsical is precisely one of the biggest charms Dragon Ball as whole has, opposed to other, more dramatic fighting shonen anime, including those series inspired by Dragon Ball.
Dragon Ball GT and Dragon Ball Super have tried to capture the same kind of charm the original series had, without success.
