What are the best or cheapest motors to use? AC or DC?
"Best" depends on your goals. You can spent $20,000 on a motor I'm sure if you're wanting a competitive vehicle.
"Cheapest", presuming you want "just a car" that can perform in the general use that a car does for most people, is a DC motor from a dead forklift. Nothing else comes close. Roughly $200 most places.
You won't get regen braking with that motor, but that's a bit overhyped. It adds like 10-15% to your range in city driving. Not a big deal to lose it.
What other components are required?
Speed controller. Batteries. Suitable throttle. Charger.
Almost certainly you'll need an electric brake booster, or something to pull a vacuum so that the brakes work.
You'll need wire and fuses and breakers and all that.
Can you use the controls along with the motor from a golf cart?
You can, but you won't get performance much above golf car performance.
You can generally overdrive most motors just fine. You just give them higher voltage. However, the controller will have a max voltage and current... there are maximums due to limits in the electronics, it costs more money to have components rated for higher, so they're usually not overbuilt much.
In general, a golf car motor is too small to power a car, even if you overdrive it with higher voltage and current and add extra cooling.
Can someone direct me to some good threads I can use in this forum?
I'd say with your basic questions what you need probably isn't specific threads, it's more overview type stuff.
http://www.ev-guide.com/component-overview <-- That's outdated, but might help you get the basics down.