I agree with rask here, your guitar is ok with out an amp at the mo... Save up yer money, so in a year's time your have enough to be a decent amp and an electric... You also might just get bored of playing guitar, and i can tell you from expreince, Playing with crap equipment can be very off putting...
however, if your gonna get an amp regeradless... I tried an "orange" amp, 10watt, and i was quite impressed.. I admit, it was still crappy, but it didn't have that "bee in jar" sound that alot of little amps have... it was £50 (which i thought wasn't bad at all), so that's around $70...
but since you have an acoustic, you should be ok without an amp...
have fun...