Pick one that matches your campaign. High magic - Forgotten Realms. Normal magic - Greyhawk. Survival is hard - Dark Sun. Pirates - go with something like Freeport. Space based - Spelljammer or borrow the Starfinder setting from Paizo.
If you know the lore and like generic sandbox its Forgotten Realms.
However Forge of the Artificer+Eberron book can be used for a magi tech pulp noir type game in Sharn. Its a bit more complicated however and may not be to your taste.