I know what Gundam is, but I've never delved deep into the franchise so I'm not quite sure where to start or what to watch. The ones I've been recommended, and seen, are:
08 MS Team
War in the Pocket
Thunderbolt
And I already know to avoid Gundam Wing and that one where it's set in the future and Gundams are used in a fighting tournament or something.
Original and Zeta are good, Wing and Seed are kinda cringe. Reconquista and Unicorn are kinda iffy for me, like or leave em. 00 and Awakening I like even though some don't.
I'd recommend original > ZZ > Char's Counterattack. And F91 and Crossbones if you can. It's a shame Tobia never got his own series, even though he's still kinda popular, plus pirate gundam.
I have never seen a Gundam show, I've just used their mechs in Super Robot Wars, so I'm biased on what pilots I like and which ones look cool.