Oh gosh! Thank you! I did not know that was a thing.
Yeah, I only found out the manga existed when I saw it on the shelf at a library, and only found out about the online version once I'd already bought most of the volumes for myself.
They're really nice hardbound volumes with plenty of extras, but they're also way more expensive than I'd feel comfortable suggesting to a franchise newbie, so having something like this to link is really nice.
The Gundam Info youtube channel has a rotating selection of shows, including all of IBO, subbed and dubbed. There's also a lot on youtube that's... not as authorized, but of course I can't recommend that you go looking.
Other than UC stuff, you can start with any of the Gundam AUs. (Although Turn A has a lot of callbacks to the other shows). For a quick "Which would I like?" summary...
G Gundam: If you want crazy martial arts and romance, this is your jam. Domon Kasshu is a jerk kung fu master with a heart of gold, sent to Earth to compete in the globe-spanning Gundam fight... and to find the mysterious man from a photograph he carries everywhere. Rain Mikamura is his longsuffering childhood friend, doctor, and mechanic, sent to help him achieve victory, which is more difficult when he's being a sullen asshole (which, early on, is common). Martial arts, conspiracies, and national stereotype mechs abound in this, the first Gundam AU.
Gundam Wing: Most of North America's introduction to the franchise, Gundam Wing is the story of five teenage terrorists from Space getting into fights without understanding anything about the politics they get involved in. Odds are, the viewer won't either, as everybody doublecrosses everybody, declares a teenage girl the Queen of Earth, and otherwise flails about wildly. A nostalgic favorite in the States, most new viewer recommendations treat it more as endearingly odd than great in the traditional sense.
Gundam X: It's the end of the world and everyone feels fine. You'd think the extinction of 99 percent of the human race would leave people bleak, but our scavenger heroes are more lighthearted than you'd expect in their quest to protect the Newtypes of Earth from those who would exploit their powers, whether the reunifying Earth government, the surviving space colonies, or a couple of psychic twin jerks. Also, there are psychic dolphins. Not localized in the US and cancelled early, X has a cult following that appreciates its sunnier-than-average attitude, but the shadow of Eva didn't ever give it a chance to make a large impression on the overall audience.
Turn A Gundam: My first series, Turn A is the go-to if you want a more pastoral attitude. Long after countless apocalypses, Earth has recovered to 1900s standards, and is in general a nice place to be, with lush rolling hills and plenty of cows. Unfortunately, attempts by citizens of the Moon to rejoin their brothers and sisters on Earth turn to violence, made worse because centuries of peace have left everyone pretty poorly equipped to understand war or its catastrophic consequences. Loran, an early scout for the Moonrace, attempts to bring peace using an ancient weapon known to the citizens of Ameria as the White Doll, and to history as the TURN A GUNDAM. If you want something with nice people trying to figure out how to defuse tensions (that sometimes errupt into mech fights) between distant cultures, this is your best pick.
Gundam SEED: Unpopular in the USA, SEED is the series that re-ignited Gundam's popularity in Japan after a long decline. If you wanted the UC, but more 2000s anime, with crude early computer-assisted animation and even more personal drama, then you're in luck. The Char and Amuro analogues even were childhood friends to add more delicious angst. Also, Kira's nice-but-unprepared attitude goes down better with some people than Amuro's frequent pigheadedness and serious PTSD. Of course, SEED's success lead to...
SEED Destiny: Hooboy. If you thought SEED was controversial, then you ain't seen nothing yet. Destiny was the direct sequel to SEED, and a part of why its tremendous success didn't lead to it replacing the UC as the spine of the Gundam multiverse. Starting out as the story of an angry teenager with a grudge against Kira working for last series's villains (who, three years after the initial conflict, are looking much more reasonable than the Earth forces), Destiny turns into the story of how Kira Yamato is always right, and he created his own army that's better than everyone. It has its fans, especially in Japan, but there's also a lot of people who hate it with the passion of a thousand suns.
00 Gundam: Moving back to the cycle of alternate universes, 00 is the child of Wing, 2000s geopolitics and the Foundation novels. Working to enforce the ideals of a Harry Seldon-like figure, a team of terrorists, lead by a middle-eastern child soldier, use their powerful Gundams to try to end global war and unify mankind, even if only by making themselves everyone else's common enemy. The first season tries to focus more on geopolitics and a wide variety of prospectives, while the second season switches to a more conventional heroes-vs-villains setup as the unified Earth government turns out less benevolent than hoped. Also, there's a movie with aliens.
Gundam AGE: Sucks. Which is a shame, since the idea of seeing a hundred year war through the eyes of one family, with three generations of conflict, is pretty cool. It just combines being stupid with being boring to create one of the least liked Gundam AUs. What's worse, the slight step up of the second generation is followed by the third generation's Kio, the Gundam protagonist who makes Kira Yamato look like Mikazuki Augus. That is to say, in less inside baseball terms, Kio's an insufferable pacifist, refusing to kill the enemy even when they're genocidal monsters, and attacking his own side so they won't harm the villains (causing mass fatalities among his supposed allies).
Gundam Build Fighters: Kids play with models. But, you know, fun. The fights are dynamic, the stakes are lowered to sports and rivalries instead of the fate of the human race, and the cast is fun and lively. The sequels may not be very good (Build Divers is terrible), but the first show is worth checking out.
Mobile Suit Gundam: Iron Blooded Orphans: Now this is the show if you want to get some blood on your face and dirt under your fingernails. The grim and brutal story of a PMC's attempts to rise to the top, IBO replaces beams and lasers with maces and back alley executions. In spite of that, though, it's also a show that takes the time to reinforce the humanity of its cast. Their friendships, loves, stupid hijinks, and general attempts to make it through the day play off the grimmer side of the setting, making it easier to care when tragedy strikes. And it will, sooner or later. IBO also tends to space out combat, with Gundam battles only coming up every couple of episodes where most shows have trouble going 30 minutes without a fight.
So, yeah. Hope that's of some help.