Say I just to a little bit of exercise (enough to have some gain), what would be the supplements I should take to maximize gain and minimize pain.
I would think Creatine, Glutamine and ALC - Acetyl L-Carnitine.
What about fish oil?
What you want does not exist. If you understand the basics of nutrition, you need a certain amount of protein, carbs and fat in your diet. Beyond that, vitamins and minerals. That's just for living, so how about building muscle?
Bottom line: if you want to build muscle you have to work hard and lift heavy things. Your body will adapt to the stresses you put on it (exercise), and in its recovery it will supercompensate to handle what you told it to do plus a little spare capacity. If you want to build muscle you have to repeatedly increase what you ask of your muscle.
If you take protein supplements, creatine, l-glutamine, etc. without putting in the work that causes your body to build muscle, they will be going to waste. Anything your body does not need is excess, and all excess is either discarded (as waste product) or stored as fat.
In short, no pain, no gain.