Depends on a number of factors like your age, how much you plan to use, for what purpose you are going to use it for, how much experience you have with anabolics, etc. etc. etc.? There's no one size fits all answer.
If your young dont waste your money! I was stupid and although I had my GH levels tested and I was a little Low I took 3iu 6 days a week for 3 months, and for as much as it cost it was the dumbest thing ive done to date.
Too get the "awesome" results you hear about your gonna have to be at 10iu a day + or have super super low levels. Either way def not worth the $$$$ IMO