Start low and slowly, and work your way up. Yes, you need to "waste" some cheap strings, but that's still a better bet than a $150 higher end racket. Also, when you practice, you do not have to finish the entire job, therefore, you can always re-use the string if you do not tie the knots each time. When I first started, I actually bought a $10 racket with a few packs of cheap string. Total of no more than $25-30 range, and enough for me to do a good number (10 to 15) demo runs.