The most important thing in strength training is to pay attention to safety. If you want to gain weight slowly, you must pay attention to the standard of action. If you want to gain weight slowly, you must do strength exercises for a month or two. Because human muscles need some time to get used to it. If you are just a beginner. I suggest that everyone should pay attention to the standard of action when practicing strength, and don't simply pursue the weight of strength. But after a month or two of weight-bearing training, you can gradually gain weight. Do I have to pay back every time I gain weight? When you can't do it anymore, you must give up. Otherwise, it will do great damage to your muscles.
Generally speaking, the weight gain is from 1 kg, or 2 kg. Don't suddenly increase the weight of 5 kilograms, and be sure to pay attention to the standard of action when doing it. This strength, you can persist for a week, if you feel that your muscles have adapted to this weight. Then you can add a little more next week. In this case, it's good for your muscles. In any case, you must pay more attention to stretching after each exercise, otherwise your muscles will be easily injured.