btw i already have sonic origins and mania

I would just say play in release order 'cause I'm one of those guys, but I'd recommend Sonic X Shadow Generations for the newest/most polished sonic game(s).

Continued from the last reply (ran out of space). If you care about story and lore, you should play Sonic Adventure and then do your best to play in release order. I will warn you though, the 3D sonic games made before Sonic Unleashed are super unpolished. Still fun though.