Unless your friends are going to give you a WARRANTY for your driveway, steer clear of their advice (if you want to keep them as friends.)
ABSOLUTELY you need a base. In fact, if you can, rough the dirt down to the proper depth where it's ready for gravel (and eventually concrete), and drive on it for a week or so. This will pack the dirt a little for you especially in the 'tire lanes' (if you know what I mean.)
Generally speaking, a concrete driveway is composed of a single gravel bed, 1 pour of at LEAST 4" of concrete, and 1" expansion joints spaced AT LEAST 8' apart.
Here are a couple of useful links. Before you take ANYONE's word (including mine), take some time to educate yourself. Once you've done that, you'll understand why the Pros charge the prices they charge. Pouring Your Own Concrete Driveway - (See the 2nd-to-last question and answer.) It has some good tips. Concrete.com - Poke around here for Instructions. Maybe you can e-mail them for Instruction.