Here's a proven muscle gaining workout that I have used when I was starting out. Using this muscle gaining workout I have managed to gain over 15 pounds of lean muscle mass over the period of six months, so I guess that results that this workout routine had delivered are not bad.
Before I'll share with you the specifics I want you to remember that it is also very important for you to make sure that you supply your body with enough building materials when you're training. There's no point to try to gain muscle if you don't follow a proper bodybuilding diet, so make sure that you consume enough calories, proteins, complex carbs and fats in order to maximise the results that you'll get!
Day 1 - Monday - Chest and Triceps
I've been training my chest and triceps muscles on the same day, because when you're performing chest exercises such as bench press your tricep muscle gets to work a lot as well. At the end of the day it is wise to combine these two muscle groups, because they work in relation to each other.
Day 2 - Wednesday - Back and Biceps
Most of the time I train my back with my biceps muscles because majority of the back exercises tend to put a lot of tension on the bicep muscle as well. Like on day one I combine muscle groups which work in relation to each other in order to maximise the results that I get and prevent overtraining.
Day 3 - Friday - Shoulders and Legs
For me this is the most intensive muscle gaining workout of the week. I highly recommend to get plenty of rest before you'll enter the gym on day three, because at the end of the workout you'll feel like your muscles were beaten to death.