You should start with Revenant imo. He is very straight forward to use and build, hes easily tanky, good dps with a lil crowd control.

Khora is my fav of the most recent tho, powerhouse with CC and tanking abilities thanks to venari. She can be built very versatile depending on play type and what powers of hers you like.

Garuda is very fun pretty interactive, she is a very close combat frame tho so have to be careful. She’s like a raw version of Valkyr and add throwing knives at the end