Why bulking phase is needed?
If you want to build muscles, the most efficient way is going through a bulking phase. During bulking phase, if you desire you can have slow and permanent volume training plus a short-term of cutting (burning fat). The time that it may take you is related to your genetic.
If the calories that you receive are more than your basic metabolism (the calories that your body naturally exhaust), your weight will certainly grow, that is the reason why we bulk.
During bulking phase, we usually lower cardio exercises as much as possible (not to zero level), and focus on receiving excess calories so that they build up our muscles.
During volume training, you inevitably gain fat. You can try to build dry and separated muscles (stop having fast food and junk food) and receive calories a bit greater than your normal metabolism which makes your progress quite slow.
Generally, you should have extra 500-1000 calories to what your body exhausts. Therefore, if your metabolism is 3000 calories/day, and you get 4000 calories/day, you are likely to increase your weight by 2kg/week. If you just start exercising, you can get 4-5 kg in the first week.
This scientific principle is unchallengeable, if you do it appropriately, and don’t fool yourself with the amounts of calories you receive, you must gain weight and volume with no room for doubt.
If you have problems in gaining weight, you should review and re-analyze your activities, and probably you will need to increase receiving calories.
You may wonder why I can’t get 8000 calories a day? I can grow muscles faster and become a giant. Well, in the first place eating that much food is hard, even though it becomes possible by consuming shakes and bodybuilding supplements.
Secondly, you are going to gain excess fat. Yes, by having 8000 calories, certainly more than 5000 will build muscles, but with that excess amount of fat that will be accumulated in your body, you won’t approach having a fit body I’m afraid, and instead of being muscular, you will be more fat.