About PhotonGI (PGI) in my opinion there aren't so much to tweak. Just turn down the photon numbers for testing and check the glossiness threshold if it's fine with your materials.
About Direct Light Cache, in my opinion, the tweaking is more needed but a bit time consuming. It's difficult to find "the right" setting and , if your scene is quite heavy, it's time consuming doing tests over tests , for example in my scene the default settings turn the direct cache computing time around 5 minutes... I was able to cut it down to 1 minutes but with loss in quality...so, at the moment, I'm putting back that cache in the restroom.
About env cache I don't have any tips or feedbacks to give you.
Anyway, as someone said, it's a good start.
In my opinion some materials seems a bit too "basic" but for testing and learning I think it's fine.