I knew a guy who tried an 8 week cycle of Sust 250 only, with one injection every five days. He dieted right though he didnt have enough calories to feed his body. He dropped tons of fat and said he felt like a million buck while on it. No side effects like acne or water retention or bloating etc.
(It was after all, a fairly low dosage)
He gained "some" mass. In my opinion he could have put on alot more mass and progressed much further with Sust if his diet was properly dialed in.
Diet is the key.
Gear is simply a tool.