+1 on The ABCs of Reloading. Even the older editions are an excellent introduction to the concepts. Get a copy and read it; 90% of your questions will be answered.
I agree with the Lutnit's comments on the economics of shotshell reloading. Maybe if you were firing huge amounts...
You're not going to save much on 5.56mm NATO or 9mm Parabellum as it's cheap to buy almost anywhere. There's no way to reload 7.62 x 39mm cheaper than you can buy it; it's a losing proposition from the get-go. Virtually everything else, you can save money to one degree or another. How much saving is a matter of how much you will spend per round making it vs how much you spend buying it - simple arithmetic.
You can get into reloading for $50 (+ the price of components) with a Lee-Loader. It uses a hammer and armpower, so it's fairly slow and laborious. It does however produce good ammo. You can spend $2,500 on top-of-the-line progressive setups that will crank out ammo by the thousands very quickly. Entry-level in between the two is around $300-400.