back in the 40s through 70s, Purdy suggested using the Colle, the French, and either the Tarrasch Defense structure or the Orthodox QGD structure (...d5, ...e6, ...Nf6, ...Be7, ...0-0) possibly followed up by the fianchetto of the queen's bishop
That suggestion has been more or less repeated by many strong players since, including Susan and also Jeremy Silman among many others.
Susan has also suggested playing the King's Indian, and I believe that remains her main suggestion as a first complete opening repertoire ,,, Colle, Colle-Zukertort, or London as White, and as Black against 1.e4 the French, and against almost everything else, the King's Indian Defense.
Another good choice instead of playing the French and QGD as Black is to play the Caro-Kann and Slav.
My simple opening repertoire and the one I play almost exclusively nowadays is Mason's Opening (the London setup with 2.Bf4) as White, Scandinavian Defense against 1.e4 the Dutch against 1.Nf3, 1.d4, and 1.c4, and straightforward principled play against everything else.
I believe I read Susan Polgar learned using the Colle-Zukertort system at White, and was successful with it I was thinking of implementing it in some games.
Is that the "best" opening system for White? What is recommended for Black as a system? I'm not sure what she used for Black.