One of the things I have done in my setting is to reorient the classes towards the factions in the setting. AD&D defaults to “adventurers” as the main class orientation, and although that’s fine for the default, the setting in particular should finesse these.

So my rangers become hunters and are excluded from much of city life, but they pick up urban tracking skills and their damage bonus is widened in its scope. My paladins become “justiciars” and are lawgivers in their House Wards.

I break the priesthood down into “temple” priests, adventuring priests and monks. All priests are freecasters, so they can cast up to their limit in spells without choosing ahead of time, and monks are a fighter subclass with higher HD, better to hit and no thief skills

Even slight variants in the basic classes can bring a lot of flavor to your game. You can see how a ranger, a paladin and a priest would get along differently in this setting than they would in the default D&D setting. Rangers are outsiders and independent of city life

Justiciars are wrapped up in it, priests can be scholarly and focused on healing, staying in their Wards and temples, adventuring priests that adopt their god’s weapons and search for acolytes and converts, or aesthetics with low level psionic style powers and combat skills

Don’t be afraid to change what’s there and see what sort of flavor it brings to your game. Nothing is set in stone, and it helps keep the game fresh.