Hathaway is a sequel after the events of earlier gundam UC timeline series, so no, don't think it's a good starter per se.

if just wanna get feet wet, probably the standalone universe shows, like maybe Gundam Witch, Gundam IBO for example.
for UC timeline, probably could also start with Mobile Suit The Gundam Origin.

Gundam Thunderbolt if you just wanna watch dark, gritty, mech fight scenes