Okay, enough having fun with this guy.
15 pounds in half a year is a LOT of progress assuming it is all muscle.
Honestly just get some good old test run either an Aromatase inhibitor (AI) or something with Aromatase inhibitor (AI) properties like masteron. Start at 500 mgs TE weekly split up into 2 injections then work your way up based on your results, sides, etc... Also get an Aromatase inhibitor (AI) and adjust your dosing based off what you need. I don't condone cheating but since you've already determined you're going to do this it is better you receive real advice.
And understand 15 pounds is very hard to gain in 6 months unless you are a complete noob, returning to the weights, just starting gear and running outrageous doses with insulin and gh, etc...