You're naturally underweight. You won't really be eating as much as you think you are. If you don't track your food numbers, you aren't likely to go much of anywhere. Especially in the long run.
2600-2900 Calories.
At least 135g of protein.
Track your weight under the same conditions once per week (e.g., every Monday morning pre-breakfast).
If you aren't gaining 1-2 lbs/week, increase your calories by 10%
If you're gaining 3-4+lbs/week, lower your calories by 10%
(^In either scenario, protein remains unaffected)
The rest is details. But if you aren't actually writing your foods down and looking up the above two things, you won't be able to be sure you're actually achieving what you're supposed to. It also allows you to fine tune things later on which will pay dividends.