Well, I know a lot of people would tell you to start with the first Gundam series. But it is quite old. Then there are the weirdos who would tell you to watch G Gundam which is....G Gundam. Then there is the Gundam that most people started with Gundam Wing. Which is just full of twinks and war crimes. Turn A Gundam has a mustache. There is the entire UC timeline which starts with the original but boy can that get silly. Seed is, well, Seed. Iron blooded orphans ha a lot of hand to hand mech combat. And the newest one, Gundam: Witch from Mercury is Revolutionary Girl Utena in space. Which is not a bad thing. I guess it all comes down to what you like. Hopefully you like war crimes because those are in all Gundam shows. There are the more "grounded" shows like the original and most of the UC timeline. There are the goofier ones like G which has a horse gundam piloted by a horse. There are ones that are really gay like Iron Blooded Orphans, Wing, and Witch from Mercury. So, what do you like?