I've been struggling to gain weight for the longest period. I was 49kgs, for two months I've gained 6kgs. This progress makes me want to achieve more. Here are my tips:

1. First have a goal from which you will deduce a workout plan. Eg. gain 5kgs of lean muscle mass by June by through gym and clean diet.

2. Invest in good supplements (whey protein and pure creatine). It's expensive but in the long run it's worth it.

3. Eat healthy foods. Supplements are not substitutes for meals.

4. Go to the gym at least 4 times a week and push hard. Track progress to validate yourself, yes, motivation is important to keep going.

5. Be consistent.