There are a ton of options out there. Two things you can take all year, without cycling would be 100 whey protein, taking within 30 minutes after your workout. Another is glutamine. Generally you take it before and after workouts, and before bed on non-workout days. Glutamine suppresses cortisol which breaks down muscle. It also releases growth hormone. We naturally have glutamine, but it is all used up for other things like your small intestines. Follow the instructions for when to take it.
Creatine would be the next thing. You cycle creatine though, like 4 weeks on, and 4 weeks off. You have pretty much three main choices for creatine: Creatine monohydrate, tricreatine malate, and creatine ethyl ester. Creatine monohydrate will give you water retention, which I wouldn't want. It is a thing of the past. It also has a slow absorption rate. Tricreatine malate has faster absorption and less (if any) water retention. Creatine ethyl ester is considered the best kind of creatine. No water retention, and the fastest absorption rate. Cycle this 4 weeks on and 4 weeks off. You should notice some nice gains. Creatine helps recycle adenosine diphosphate into adenosine triphosphate. This means your muscles have more ATP available to them, which is why you'll notice your ability to workout harder. You'll experience increase in endurance in your workouts, and should be able to lift a little more/harder. Again, follow the instructions on the product you get on when to take it.
To add to creatine's effect, you can take ribose. This helps produce more ATP, but in a different way than creatine. With more ATP, more ADP can be recycled into ATP. Stacking these two in the same 4 week cycle will give you even better gains.
Another thing you can consider is HMB. Studies on HMB show that people have gained lean body tissue while lowering body fat percentage. Again, studies have shown that when combined with creatine, the effects are even greater. However, you won't be able to infinitely gain muscle in a certain period. I would just stack the creatine and ribose for 4 weeks, then when you're off of those take HMB for 4 weeks.
Other than this, make sure you have a very good diet. These are only supplements remember. Without a good diet, you won't get any good gains. If you don't have time to get enough of what you need because of your schedule or something, you can take weight gainers like prolab n large. There are lots out there though.
So in sum: glutamine and whey protein taken all the time. Cycle creatine + ribose stacked, possibly HMB while you're off of those. And a GOOD DIET. A good diet will help you the best.
