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.
08th MS Team and 0080 War in the Pocket are my favorite Gundam franchise entries, but they both are more impactful with a better understanding of the universe those series exist in.
The original Gundam is on the longish side and probably a bit dated in terms of character designs and pacing, but it's still the best place to start. I'd watch the compilation movies if the episodes are a bit too much of a commitment for you, or at least read some detailed summaries.
G Gundam, the fighting tournament series, is extremely goofy. Others love it, but I hated it. I have good memories of Wing, but I'm very doubtful it would hold up if I were to watch it now.
Enjoy!
FWIW I rewatched Wing back in either freshman year of college or senior year of highschool, years and years after watching as a kid either way and I thought it held up.
But I'll be honest the main draw for me is the aesthetic. I love how all the uniforms and mobile suits have this diesel-punky Inter-war period feel to 'em.