I think that from a gaming perspective (rather than collecting figures) a lot depends on what you are trying to achieve. If you want totally Potter experience with chits and cards which have the “look”, I suspect it’s the official game or to use the pieces in a home grown game.
I painted up a few figures that will do as approximations of some characters and a few that look like vaguely eccentric wizard types. I then pitched two wizards and their loyal groundsman against a D&D troll and a D&D giant weasel which I called a bandersnatch. I used a version of EDNA to track general health and ability with each wizard having three powers each of which had a turn to recharge. The groundsman had a large axe....
Good fun but I’m still working on it