Need more info
Gas or electric?
Electric:
www.hpi.com
www.teamxray.com
Gas:
www.hpi.com
www.serpent.com (I have all their gas cars) Top of the line products which you will not regret)
300 dollars? american
if so keep saving till you get another 200 dollars. RC season is almost over except for electric.
Electric you will need to get a quick charger.
Integy makes the best ones but at 300 for the nice one that might be a little expensive for you but they make a cheaper one for about 100 bucks.
ESC electric speed control LRp makes a nice one. but there are a lot of others out there.
batterpack depends on the type many to choose from
modified motor.
Gas or nitro cars
You will need to get nitro fuel, glow plug, starter box for the non pull engine. Nitro engine .12 if you are going for the 200mm class
Both cars will need a remote JR x3 is a decent remote R1 for the serious in mind
too many things to list but those are some of the basic.