G is a bad place to start tbh. It's goofy awesome at its best, but it's also long and episodic and gets repetitive and boring outside the lolz factor. G is a great place to be after you're cool with Gundam and want something silly fun.
Now if G Gundam had been a 7 ep OAV like Giant Robo I'm sure it'd be 100% perfect from start to finish. But at 50 eps...yeah.
I wouldn't recommend anyone trying to get into or check out Gundam start with a 50 ep series. That's just way too much commitment and 50 eps shows are gonna have good & bad. Like Iron-Blood Orphans has a fantastic first 13 eps and excellent finish in the last 13 eps, but you still gotta go through a rough middle 26 eps (13 hours!) of stuff in the center.
Watch:
Gundam Movie trilogy - 3 movies, easy to digest, still great, best basis for main gundam timeline
0080 - Short 4ep OAV that's about peoples and not robots
0083 - 13 eps kinda mediocre but flashy Top Gun of Gundam. It's short enough that it's worth watching for the turn your brain off watch cool mecha explode
CCA - single movie, you kinda should watch Zeta Gundam (50 eps) before it, but eh, you can watch Zeta later and just enjoy Nu Gundam and sick animation and the ending to the Char/Amuro rivarly
Unicorn Gundam - Don't watch this before watching at least the Gundam Movie trilogy & CCA, then watch this because it's all over the place, but it's short at 7eps, the animation and mecha are awesome, and the last ep is 40 mins of beautiful mecha nonsense.
If you want to get into the long ass TV shows after that, then Zeta, Iron-Blood Orphans, 00 S1 and then bail because S2 is shit (ignore the movie too), G Gundam, Turn A Gundam, Gundam X, Wing TV + Eternal Waltz are all solid watches.