Start with a full kit (including chassis and possibly headshell) if you can. Plenty of stuff to chose from, from the simplest Fender single channel to full-sized Marshall and SLO. Obviously easier amps will be easier to start on but doing something more complicated is doable if you take your time and try to go beyond following instruction by trying to understand why you twist certain wires, why V1 should stay the hell away from a power transformer, etc. You could paint some kits by numbers but that might not net you the result you are hoping for.