I personally would recommend viewing the UC stuff in chronological order. There's numerous references to events in later series as well a progression to why the plot moves the way it does. Additionally, technology (for the most part) progresses upon itself in a way that will seem odd if you miss something.
Sooo...
Mobile Suit Gundam
08th MS Team
0080
0083
Zeta Gundam
ZZ Gundam
Char's Counterattack
Gundam Unicorn
Gundam F91
Gundam Victory
That said, the major plot points would be:
Mobile Suit Gundam
Zeta Gundam
ZZ Gundam
Char's Counterattack
Gundam Unicorn
Everything post Unicorn is set enough years in the future that it could be considered a side story, though it's technically not. Crossbone Gundam, as mentioned before, follows F91... but to my knowledge it only exists in Manga form. Shame too because it's amazing. 08th MS Team and it's ilk are filler stories that mostly show different view points and fill in gaps in technological progression.
Sooo...
Mobile Suit Gundam
08th MS Team
0080
0083
Zeta Gundam
ZZ Gundam
Char's Counterattack
Gundam Unicorn
Gundam F91
Gundam Victory
That said, the major plot points would be:
Mobile Suit Gundam
Zeta Gundam
ZZ Gundam
Char's Counterattack
Gundam Unicorn
Everything post Unicorn is set enough years in the future that it could be considered a side story, though it's technically not. Crossbone Gundam, as mentioned before, follows F91... but to my knowledge it only exists in Manga form. Shame too because it's amazing. 08th MS Team and it's ilk are filler stories that mostly show different view points and fill in gaps in technological progression.
My life is a chip in your pile. Ante up!