So Im thinking of just having it set on the "wild frontier". The King looking to expand etc.
I may use the Keep from Keep on the Borderlands and have the Caves of Chaos as an option. Toss in Stonehell and Barrowmaze and Castle of the Mad Archmage at later points. Learning of different dungeons via patrons at the Tavern or via a talkative guard whatever.
Like, have a small dungeon they can "do" like Caves of Chaos (then maybe Silver Princess, and then etc etc maybe the whole B series) and then 2-3 Deep Dive options they can explore as they wish.