The first build-thing is Model Suit Gunpla Builders Beginning G - Which is a pretty short OVA series that serves mostly as a proof of concept for the later series. It's entirely disposable, but it's a cute little ode to the hobby.
Gundam Build Fighters - A decent show with some serious moments, but is mostly a low stakes, amusing rhomp through a lot of self-congratulatory fan service that celebrates all the cool robots and other aspect surrounding the fandom. It's filled to the brim with references and tropes that touch upon almost every corner of the franchise. It's a good of a place to jump into as any, and will probably be a good barometer if the rest of the Build shows are worth your time.
Gundam Build Fighters Try - Is the Zeta Gundam to the original Build Fighters. Taking place like 7 years later, following a different cast of characters in the same world. Same basic scenario, minus some of the more fantastical fantasy bits of the original show, and focusing on 3v3 battles instead of 1v1. I had a lot of fun because it wants to be a spiritual successor to G Gundam, it has a much more likable cast, and takes the "Gunpla is Freedom!" mantra of kitbashing whatever you can imagine into the extreme. It is a bit more polarizing show among fans, who wanted a more direct sequel. I enjoy this show more than the former, but I feel like I'm in rare company with that one. It's also a bit more horny than the first show which is a big disappointment. It also opens up seeming like it might have a female lead, and then she quickly gets shoved aside by a boiler plate male co-lead which felt like a cruel bait-and-switch. (Fumina is a fun character and was wronged by the show.)
Gundam Build Divers - Is a soft reset and takes place in a nebulously different setting where something like Build Fighters happened, but then they democratized Gunpla Battles by making it all digital and online so everyone could play from the comfort of their own homes. The story itself and the characters are generally not as strong as Build Fighters, and the show itself is pretty consistently panned by fans. But I enjoyed it, and I enjoyed where they took the story regarding sentient AIs It's also worth noting that Build Divers and its sequel are imminently less horny for underaged teenage girls than their predecessor, which is a big plus in my book.
Gundam Build Divers Re:Rise - Is another Zeta-style sequel following a different cast in the same setting several years later. I don't wanna spoil anything, but while four previous things I described are essentially feel-good, navel-gazing, elaborate toy commercials, Re:Rise is a legitimate Gundam show and the best Gundam thing in the franchise since G-Reco. If you bounce off of Build Fighters or any of the other shows, at least give this one a try. It builds upon the foundations of the original Divers, but nothing happening in it is so complicated that you couldn't figure out what's going on by the context clues and the show doing callbacks to the original.
Gundam Breaker Battalog - my understanding is that this isn't a real show, but a collection of short vignettes that tie into a mobile game that tries to be a facsimile of gunpla battle. I haven't bothered watching it yet, but I'll get around to it eventually.
But seriously, it's the best Gundam thing since Turn-A, it's a must watch.
) Their anime/character lines are mostly really good too/a lot of fun to make. And lately they've been branching out into all kinds of interesting, quirky kits like this meticulously designed 2:5 scale PS1: