You could probably see some decent gains from 300mg a week. I don't think you'll gain 15lbs of lean mass but you can try.

What do you have lined up for pct? I would wait to cut BF until after pct so either use your clen during pct while still eating alot of cals or use it after pct to drop some BF. Don't try to cut BF during pct or you'll just lose the gains you just made.