Free weight exercises, such as squats, dumbbell presses, dumbbell fly, bench presses, bent over dumbbell row, and others put a lot of stress in the supporting muscle groups, which is why you get tired really fast doing free weight exercises. However, even if you do get tired really fast, you will gain more muscles and you will become a lot stronger at a very fast rate.
You can include machine exercises in your program but you need to do it after you execute all the free weight exercises. This way, you will be able to take advantage of the strength you have on free weight exercises and not deplete it on machine exercises.
If you are a beginner, concentrate on lighter weights. Your primary goal is not muscle gain yet. You first need to properly execute the free weight exercises you have in your program in order for you to move on to heavier weights.
Concentrate on strengthening the supporting muscles first and when it is able to support the weight you are lifting and that you are able to execute the free weight exercises properly, then it's time for you to concentrate on the primary muscles.
Also, in order to build muscle mass, you need to lift heavier weights. What heavy means is that weights that are challenging for you and weights that you will be able to lift with 8 to 12 repetitions for 3 sets. If you can do more than 15 repetitions before temporary failure sets in, then it will be considered as light weight.
Remember these tips and you can be sure that you will be able to gain muscles fast. Always remember that one of the keys to muscle gain is to strengthen the supporting muscles. And, only doing free weight exercises will be able to do this efficiently.