it sounds like the problem is your diet and possibly your training. lets start there. then we'll get into steroids. you should be eating around 1.5 to 2 grams of protein per lb of body weight. steroids mainly work by allowing your body to store protein in the muscle faster than when natural. devide up your overall protein into meals every 2-3 hours a day. if you aren't giving your muscle enough protein, you wont build any real amount of muscle. you may gain some weight while on, but that will mostly be water weight that you will lose when you come back off. you're going to need to get this in order before you consider AAS. 

if you dont already have that in order, you'll want to spend some time getting yourself trained to eat right before you move on to gear, you should spend at least 1 yr working on this and getting it right. many people would suggest 2 years. 

when you're ready, you should consider a cycle of test e around 250-375mg test a wk for about 10-12 wks, along with a low dose AI like arom and a solid PCT of nolvadex starting 2 wks after your last inject. get the diet in order first and you will gain very well on this cycle. i use a lot of GP brand gear. the test e is strong and will work very well for your needs