If you are a hard gainer like me, you should minimize your cardios to like 1-2 times per week, and each cardio workout no more than 20-30 mins. You are trying to gain weight, and not the other way around. So you say to yourself that you are going to get fat then. It is impossible not to gain body fat percentages while you are trying to gain weight. No matter how strict you follow your mass training program, you will gain some fat.

Only when you are satisfied with how big you are, then you would follow a strict diet plan and exercise program to reduce body fat and maintain muscle definition. By doing cardio 1-2 times per week and no more than 20-30 mins per section, plus total body mass training, you will minimize fat while you get bigger in muscles.

Some hard gainers won't even do cardios at all until they decide they got big enough, and start doing cardio and follow a strict diet. This method you would have more fat to deal with when you are trying to reduce your body fat percentage.

When you do cardio, make sure it is an intensive and quick workout. Go as fast as you can until you need to stop. Slower pace for a minute. Repeat by running fast. Slow. Fast. Slow. Fast. You get the point. This method revs up your metabolism. By running at a steady pace, you will not increase your metabolism. By constantly changing your pace, you are playing tricks with your metabolism, and your metabolism would be in full-speed for another 10-20 hours while you are sitting at home watching tv, sleep, etc.

If you ask me how many times I do cardio per week, I would tell you some weeks are 0 and sometimes 1-2 per week.