As a whole: it's all Dragon Ball, like how Shippuden is with Naruto.
Most of the time, DB is entertaining wherever you start (one reason why starting from its "Part 2" wasn't difficult to pick up for 90s kids).
That being said, its present day, and we have access to all of the DB series now, so there's no reason why it can't be experienced in its actual order.
Also, if you're watching it in English, be aware the dub for DB is a tad dated (better than Z's though, as it was dubbed around Z's end) and the non-dialogue audio is mostly mono. Its 153 episodes (there's a little filler but not nearly to Naruto level) and its full of charm. It's cool to watch the standard being set for shonen franchises when recognizing the tropes it inspired.
After DB you have a couple options: You could watch Z, or you could watch Z Kai (the 2009 revision).
Be warned that Z has quite a bit more filler than DB did, and the pacing has some issues. A majority of its audio is also in mono. It's 291 episodes.
Also, if you're going for English dub, Z's is kind of a mess. Its all over the place for a myriad of reasons. For instance, some characters are not portrayed accurately and some outdated dialogue misconstrues some important things.
Option B is Z Kai, which cuts out nearly all the filler and corrects most of the pacing issues of Z, landing it at 167 episodes compared Z's 291. The audio is all stereo, the footage is remastered (at times in jarring ways but nothing too bad), and the English dub is GREAT, much better written and acted than Z's. Kai is the preferred way of many English dub fans to watch the show.
GT is an anime-original and was the first attempt at a Z sequel in the late 90s. Original author wasn't too involved. It's polarizing but always an option to watch, many people feel different ways.
Super is the current sequel with the original author contributing a little bit more in terms of story outlines. It's quality can vary, but it's pretty fun post-Z stuff, IMO. It's English dub is much more in-line with Kai's, so Kai is a good transition to Super if you wanna watch it dubbed.