G gundam is my favorite but not like any other in the series but I still recommend. Also Gundam Wing and Iron blooded Orphans

Except for the first four seasons, all the subsequent Gundam season are set in separate universes. You can start with either of them really. For a more “modern” season, I would say the best is Gundam 00, if you are willing to go a bit further back, there is Gundam SEED and Gundam Wing. SEED is the only season beyond the original 4 to get a direct sequel so that tells you how good it is. Beyond that, there are movies set in the same universe as existing seasons, depending on their popularity.