Here some ideas I had for my mod.
Raw materials:
Vanilla buildings need 1 boulder. Easy.
Custom building can use all kinds of stuff, if you need 20 items it gets a lot harder. If these items are high tech already, like soap, steel, rare gems... then you can only build these buildings easily in a big, older fortress, OR you have to actively work towards it.
Magma:
Magma automatically enables magma buildings. Make a normal building, with normal reaction, but make only a magma version of it. This way only fortresses that dug deep, (magma lake) explore (magma chute) or start at a volcano, have access to the tech.
Use Narhirils system:
A reaction that has a low chance of producing a special item that is needed. If the reaction needs reagents, it is a lot harder.
Item drops:
Use items only dropped by special creatures. This way you have to hunt/fight to advance your race. (I use it with cavern creatures (blobs) for special ammo, and semi/megabests (for a reaction that turns a dwarf instantly legendary in one skill) These items can be bodyparts from butchering pets, special egg types, or special corpse types.
Trading:
Make a special item only aviable to one race. This way you have to trade with them to get the better goods. I use this for warbeasts (elven) constructs (dwarven) and 2h-weapons, towershields and platearmor (human)
Hell:
Make a special item only aviable in hell, like an itemdrop, a plant, a tree, a pet, whatever. This way only a civilization strong enough to fight demons get access to the tech.
I hope that helps