From a learner's perspective, the first bit of vocal home recording I did was without a compressor, and so I had to raise and lower the volume of the audio in the software to control the dynamics.
Software nowdays has some pretty good virtual compressor plugins, but in order to be able to control the dymanics on the way *into* the computer (mainly to avoid clipping the signal too often) an outboard compressor is a very useful tool.
I don't know what the conversion rate is like for where you are, but here in Aus, the cheapest compressors are the behringer composer pros for about Aus$200 (retail).
They are OK to get you started and are pretty good value for money (unless you get a dodgy unit, which seems to be a common complaint amongst forum members)
Dags