The best you can do is help them install uBlock Origin and FB/Insta Lite (not great options, but better than the mainline apps).

You don’t need the other service. I personally strongly oppose pitching stuff about federation and so on (this is something for a user to look into if they are interested).

If you are looking for communities, click the all Communities -> All Communities button:

https://piefed.social/communities

And then type a keyword to find a community.

Voyager works for mobile:

https://f-droid.org/packages/app.vger.voyager/

You can also just use the mobile website (that’s what I prefer).

If you have any questions, just post them here:

https://piefed.social/c/piefed_help