It is very important to eat mostly healthy foods or follow a gaining diet if you are trying to gain weight.
If you want to gain weight slowly and steadily, then aim for 300-500 calories more than you burn each day according to the calculator. If you want to gain weight fast, then aim for something like 700-1000 calories above your maintenance level. Keep in mind that calorie calculators only provide estimates.
Your needs may vary by several hundred calories per day, give or take. You don’t need to count calories for the rest of your life, but it helps to do it for the first few days/weeks to get a feel for how many calories you are eating. If you are concerned about your physical health, Here is a full healthy diet plan for you that should be followed every day