Hello dear,
First of all, please do not be in a hurry to gain weight.
Given the history, as you are experiencing difficulty in gaining weight, it will be better to rule out causes of
underweight.
Investigations like
complete blood count,
thyroid profile, estimation of blood sugar level will be helpful to rule out any chronic infection,
hormonal and metabolic causes.
Moreover, you should not compromise on routine healthy food such as:
1. Consume more of natural diet like fresh fruits, green vegetables, milk, eggs, wheat, etc.
2. Avoid oily and junk food.
3. Stay away from smoking & alcohol.
Wishing you a healthy life.
Take care.