You can get just as good without a coach as you can with a coach.
However, you will do it MUCH faster with a coach.
I don't really agree with that...all you need are a few friends about your strength going to tourneys with you and looking over each other's games (that's what I did...and we all made it to 2100 at least). Save your money...at least until you're good enough to really merit a coach.
The pickles are very important for this.