I used to own a bodybuilding supps company, so I have some definite thoughts.
First, eat lots. You need the calories more than you think. Carbs are not your enemy when you are trying to gain. It seems you are eating clean, so that's good.
Second, train intelligently for your body type.Maybe you need 5 reps with heavy weights instead of 8 reps with medium weights. There is a case to be made for each method. A qualified trainer can help with that. Also use the internet to find as much training info as you can. Here's a site with lots of great articles from top trainers. http://www.t-nation.com/
Third, even though I owned a supps business, I have a belief that most supplements are not very useful and, that being said, they are also not cost effective because of the amounts you need to take to get results. Skip the nitric oxide booster (hemodilator), HMB, CLA, and all the other junk. If you want to stay natural, skip the prohormones. If not, be aware that they essentially metabolize into real hormones, so you will be exposed to similar side effects if you take enough to be effective. In that case, you will need to have access to estrogen blockers. Anyway, if you are going to use pro-hormones, you'd be better off saving your money and using the real ones. Milligram for milligram, real hormones will turn out to be cheaper and many times more effective. But, whether to use pro-hormones or real hormones is a decision you have to make. I am just saying that if you go that route, why do it the half-assed way with pro-hormones? Well, I guess there is a legal issue, duh.
Here are some things you should use, no matter what:
1) High quality protein. I prefer a whey concentrate/isolate blend. I know it's against common wisdom to not prefer pure isolate, but the process of making isolate strips out important immunoglobulins. And good concentrate, hopefully used by the better companies is 85% protein, while isolate is between 85% and 100%. Not sure the extra purity of the isolate makes up for the loss of important co-factors. They both absorb at the same rate. I, too, am a big fan of muscle milk.
2) Glutamine. The king of amino acids. Necessary for muscle recovery and repair and building.
3) BCAA's. I use a really good one, the NSI brand from Vitacost. The ones like this brand and Optimum have double the normal amount of L-Leucine - needed when you are over 40. Under 40, you can get away with normal ratio BCAA's. I think liquid BCAA's are better than capsules.
4) Use a natural testosterone booster if you decided against pro-hormones or real ones. There is a new-ish product on the market, MyoGenX, which uses Fadogia Agrestis. It is like Tribulus Terrestris but the reports that I've seen on it show that it might be superior. I've tried it and I like it better. Tribulus (standardized with high furostanols and saponins) is sort of a standard. Fenugreek is another source of furostanols and saponins. There are some products that blend tribulus and fenugreek.
These first 4 are definites.
After that, I'd consider using ZMA for muscle recovery and repair. Nice to have, but not a necessity.
I am not big on creatine, but it won't hurt you. It is useful in hydrating muscle cells (makes you look bigger) and giving an energy boost, but some people have gastric upset from it and research suggests that it stops being effective after 6 weeks. So, you could cycle it. The point being, if it helps with energy, that means you can lift harder, and the harder work that will cause your muscles to respond with growth. If you are using pro-hormones or hormones, creatine is not necessary.
Stepping down another level, there's deer antler velvet, as a source of IGF-1. IGF-1 helps create new satellite muscle cells. There is some evidence that Deer Antler Velvet is mildly effective, though nowhere near using LR3 IGF-1 peptide. On the other hand, if you figure the cost of taking enough deer antler velvet compared with real IGF-1, maybe the IGF-1 is not so expensive. Along those lines, bovine colostrum is touted as being able to act as a myostatin inhibitor (another method of causing muscle cell proliferation). It's hard to prove those claims though.