If you are going to get into Gundam, I highly suggest starting here. Pretty much every single Gundam series out there is rooted in characters/gundam from this time line. If your a newer anime fan you may find it difficult to get into the animation. Hang in there, the story and historical reference is well worth it. In order they are:
-Mobile Suit Gundam
-MS Zeta Gundam
-MS Gundam ZZ
-MS Gundam 0080: War in the Pocket
-MS Gundam F91
-MS Gundam 0083: Stardust Memory
-MS Victory Gundam
-MS Gundam 08th MS Team
-MS Gundam Unicorn
-Turn A Gundam
After Colony Timeline
This is probably where most of you were introduced into the Gundam world. A group of space colony scientists build Gundams piloted by young boys in hopes of weakening Earths oppressive Government. Is it the best Gundam series? Not by a long shot in my opinion. Will the vast majority of Anime fans tell you its the best Gundam series? Probably, although Unicorn is making a solid play as a fan favorite (Gundam Build Fighters seems to be popular as well but I have not watched it).
Cosmic Era Timeline
If the Universal Century seems to “old” for your tastes, this is a great place to jump into Gundam. While I am not a really big fan of Gundam SEED, the series does highlight some of the qualities of the UC timeline and make it more palletable for the modern viewer with a much more 21st century animation style.
-Gundam SEED Destiny
-Gundam SEED MSV Astray
-Gundam SEED Stargazer
After War Timeline
Welcome to your post apocalyptic Gundam universe. The X is one of my favorite Gundam in all gundam universe to be honest. Basically the series take place after a giant colony is dropped on Earth, wiping out almost the entire population.
Future Century Timeline
The ever dreaded Future Century. Just about ALL hardcore Gundam fans will shun this series. Me on the other hand? LOVED IT. Instead of giant wars and colonies fighting one another, rulers are decided by a Gundam tournament that occurs every 4 years. This one isn’t for everyone, but some of you just may like it . . dar I say love it?
Anno Domini Timeline
This is bleh bleh bleh. Ok if you liked Gundam Wing then your probably going to like this one. Several factions are constantly vying for power when a mysterious group known as Celestial Beings creates Gundams that are years beyond an current MS technology. So on and so forth.