I'm in the same boat, I get test cyp for TRT. You can use it for gains but it all depends on how often you have your bloodwork. You don't want to walk in with 10x the level you should be at. Finding a doc to prescribe it these days is hard enough (everyone wants to give you the cream).

I run it 2 cc's per week and it definitely keeps up the sex drive and as long as I watch my diet closely I make decent gains. You could go 1.5 to 2, just make sure you taper back off a few weeks before you go back in so your blood levels will be where they should. Since it's basically a never ending supply you can play with it some to see what makes you feel the best without any sides. At 300-400 mg a week you should be well outside the range of most sides.