If possible avoid creatine - still largely unknown.
Don't listen to this, please.
I have been lifting since junior high, but I only got into it hardcore about junior year of high school. For the past 4 years I have been to the gym about 5-6 times a week and have extreme gains and ridiculous results. Creatine is the safest supplement around and has been tested for about 20 years. Assuming you take creatine in the right dosage and stay hydrated you will get great boosts with no side-effects. I have used it for 4 years and have never had a side effect.
As far as supplements, you absolutely need whey protein if you are serious about this. You'll need a minimum
of 120g of protein per day if you lift hard and you will not be able to achieve this consistently without whey. Creatine is amazing and works very well. Use it everyday, even on rest days in the morning. Only two problems I have found with creatine: A) Although studies show that your body cannot develop tolerance to creatine, I swear I have. When I started I used to feel like I was bouncing off the walls after I took it, all I wanted to do was pump iron and I had adrenaline at high levels through my workout. As years passed that feeling has been curbed. B) If you stop taking creatine, you will feel weaker (mentally) at the gym. I had days where I didn't even want to lift if I was out of creatine because I felt weaker without it. If you have anymore money, glutamine is amazing, but I can't afford all three and I take creatine over just about anything. One thing I recommend I staying away from Nitric Oxide, I tried it out based on recomendations from pro bodybuilders and after two doses I felt like my heart was going to tear apart.
As far as workouts go, remember, theres a difference between lean muscle and big gains. I assume you want gains cause pretty much all guys do. In this case, you need to do more weight, less times. Don't listen to this 12 rep BS, do 4 sets, 8 reps at the highest weight you can. I have excercises where I cut down to 6 reps at times. I read a very nice article which opened up my eyes a couple of years back (I used to do the whole 12 rep thing too, much less gains): The article simply stated that it is common sense to think that if your body can handle 240 reps (20 sets x 12 reps), you're just not doing enough weight and making it easy on yourself. If you're doing anything more then at most
150 reps on one muscle group per workout, you're just being easy on yourself.
If you have any other questions, I'm always here to help when it comes to this issue, I have been around the "business" for a long time now