As far as effect pedals go, the compressor pedal is mostly a specialty tool. It will depend on how you like to shape your tone if you aren't the most accurate guitarist or just aren't concerned with it than a compression pedal might not be the most useful tool to have in your arsenal. But on the other side of the pond if you are aiming for perfection and to hit every note accurately you will find a compression pedal a godsend. This means that if you are just starting out setting your pedalboard, you don't need to worry a lot. While it might be beneficial to you in your quest for setting up the perfect tones for your needs, it is not the most crucial. There are different pedals that you will need to buy before a compressor pedal, and after you are feeling confident about your playing and have created your style you may start looking at compressors.