Thinset Cement

Or should I put on a layer of thinset and let dry overnight, then put on another layer of thinset tile and let it dry and then grout?

Ideally, you want to put a layer of leveling compound, followed by a leaf-range (sheet of laminated paper), then let this set overnight. Then you put the thinset and tile on the sheet pallet. The Slipsheet allows for differences in thermal expansion between the concrete and the floor. This prevents cracking of tiles and grout uneven expansion and contraction of materials.