ESC (Electronic Speed Control) - as you are new I would recommend one that has reverse. Expect to pay 50 on this.
Battery pack (I assumed its an electric) - you can get like a 1500mah 6 cell for about 10-15. It should last like a quality 10 minutes or so. Then theres the mid range 1800mah and the pro level 3000mah. Oh, and theres the 'matched' cells which offer top of the line performance at a cost of price.
Charger (duh!

)- would really depend on what you really one. Timed chargers are basically timed to charge until time = 0 (like Microsizers charging for 45 seconds). Peak charging charges the pack until full. They range from about $30 and beyond.
I think thats it. Haha, I sound like I'm experienced with this stuff even know I never owned and R/C beyond something like 1/18 scale (no, its not a HPI Micro RS4; I'm the low budget R/Cer!)