depends on how many mg per week that you want to run
If you plan on 250 per week then you only need eight...if you plan on 500mg's then multiply by two...750, then ....you get the idea
300mg * 8 wks = 2400mg total
2400mg total / 250mg per ml = 9.6 amps to be exact
So get at least 10. Like nycspike said, you may want to increase the dosages after a few weeks