I agree with Jerry, Pixel + Graphense OS seems to be the best way to go.
You bank apps may just not work properly though (if at all) without google services, or they also might work. It is a bit of a gamble every time while installing a bank app, it depends how the app has been coded to rely on google.
In any case, graphene made these sandboxes user profiles, where you can decide to install google services for apps that really need it, very useful. In there, the OS also limits how google runs the show and therefore google remains less invasive than︀ on a stock android phone.