Tuna will help, but it sure does not equal 1 pound of muscle. A can of tuna contains around 40 grams of protein, no carbs, no fat.
Mizong_Kid,
Basically, you are what is called a hard gainer. You have a faster than normal metabolism, so you have to eat more and smarter than the average guy as well as lift weights. Your muscles won’t grow unless you stress them enough and force them to adapt. That’s all bodybuilding and powerlifting is: creating the right stimulus so your body undergoes a very specific adaptation. Hey, it’s the way of life.
A very simple formula for gaining weight and mass would be this:
Total calories you eat per day = your weight x 18
These calories should be split into 40% protein, 30% carbohydrates, 30% fat.
This is where is gets kind of complicated: protein = 4 calories/gram; carbs = 4 calories/gram; fats = 9 calories/gram.
For example, on a 3,000 calorie/day diet, that would be 1,200 calories from protein, 900 calories from carbs, 900 calories from fat.
To find out how many grams of each this translates to, it would be 1,200/4 = 300 grams of protein; 900/4 = 225 grams/carbs; 900/9 = 100 grams of fat.
You will also want to split this intake into 6 meals. 1 meal right before and after your workout, and the other 4 meals every 3 hours until bed. This will prevent your body from going catabolic (nutrient deprived) because it will start to eat your muscle at that point.
To lift weights, a simple 3 day split would do the trick.
Day 1: Chest and arms
-Chest -Tricep -Bicep -Forearm
*3-4 sets of 8-12 reps each
Day 2: OFF
Day 3: Legs
-Goodmorning/Squat/or Deadlift -Calve raises (calves = 3xreps)
*3-4 sets of 8-12 (24-36 reps for calves)
Day 4: OFF
Day 5: Back and Shoulders
-Pull-ups & rows -Overhead presses
*3-4 sets of 8-12 reps
Day 6&7: OFF
Do 3 - 6 sets per body part and concentrate on the lowering motion. Count to 3 when lowering the weight, and to one when raising it. This is what we call a 3/0/1 tempo.
This may seem complicated to start, but it’s the most basic protocol to follow for gaining muscle mass. If it was easy, then you’d see a lot more people walking around with muscle. You will have to alter the number of calories needed depending on how much cardio you are doing. The more cardio you do, the difficulty of gaining weight goes up exponentially.
Dear other forum members,
I know this is a body building routine ::gasp::. 
I just think it is an easier way to gain muscle mass than to explain the powerlifting conjugated periodization approach. He will gain a little fat on this program, but there is no way to gain a significant amount of muscle without some fat too.
When training for mass, training to failure once every 3 or 4 weeks isn’t bad. To do so all the time would be detrimental to your development.