What stereo system to put in my truck?

I am 16 and just got my first car. i have a 1993 ford ranger sxt pickup. supercab. i have about 300 dollars and want a good stereo system. should i just get a new head unit and 4 speakers (two front two rear) or should i get head unit, amp, subwoofer and new speakers. i also would like to know where to put them. what should i buy and where from. thanks