youve watched some good ones so far.

Definitely go for Gundam Iron Blooded orphans. Gundam Wing. and other ones. the old series are also good to get a better understanding of Unicorn's story. The original Gundam series, Z Gundam, ZZ Gundam, Char's counter attack, Gundam Stardust memory, Gundam F91 and the like.

Once youve watched those, go ahead and indulge in the Gundam Build series!