Although GrapheneOS puts a lot of work into sandboxing and protecting against Google Play, don't assume that you have to go that direction.
An alternative direction, if you wish, is to simply minimize the set of apps you use. And maybe it turns out that you don't really need anything from Google Play.
For example, I limit myself to a few open source apps (e.g., email, TOTP authenticator, maps, calendaring).
Anything else, either I don't need to do it from my phone, or I can get by with the Web site version of it in the phone's Web browser.
I also recently went through and deleted some open source apps that were a good idea to try, and which initially seemed like a good idea to keep on hand, but that I really wasn't using, and didn't expect to use without opportunity to reinstall them, so were just clutter and risk (e.g., Matrix, XMPP, Signal).