Start from the signal and power needs, not from a layer count. A simple controller may need four layers; a dense board with BGA fan-out, controlled impedance, or mixed analog and digital sections often needs six to ten.
Material follows the application: standard FR-4 for general electronics, high-Tg laminates where the board sees repeated heat cycles, low-loss laminates for RF and high-speed links, and aluminum or copper base where heat has to leave the board.
Send your stack-up target, impedance requirements, copper weight, and surface finish together with the Gerber files. Our engineers review them before quoting and point out anything that adds cost without helping the design.