I have paved a few driveways in my day. I worked as an estimator for a road building company after I did my engineering tech in college.
If you have clay you want to go about 2' down. geotextile on that is a good idea. It keeps the clay from boiling up into your gravel base.
If you are lucky you will have some slope to the road and when things get wet your new gravel will drain down to the road. If not, the hole you dug in the clay will fill like a swimming pool and when it freezes its going to move.
Weeping tile down each side of the paved area is a good idea.
Assuming you have good drainage you compact 18" of pit run gravel into your hole, then 6" of granular A on top.
Then whatever top you want on it. Stone dust for your brick, concrete or asphalt right on top. You gotta adjust your depth of excavation for the thickness of whatever you put on top.
If you are in sand or well drained material you want to go with the 6" of granular A. Kinda depends on how solid your existing ground is. If its soft you may want a bit of pit run in there too. You need a solid base thats drained to keep the top from moving. Granular A is graded to pack very hard. The pit run packs and drains well.
It sounds like I am rambling but drainage is key. If it doesn't drain you should go with interlocking brick because when it heaves you can take it out, relevel the whole thing and put it back again.