I can suggest to drink coconut water daily in the morning at empty stomach.Eat banana with milk so that these two help you in gaining your weight.So that you can get resistance.
For gums daily brush two times one in the early morning,next before going to bed.Use salt to clean your teeth soon after you cleaned with paste.you have to eat continuously so that gums will be reduced.
I am not sure how you are in trouble but these are the tips normally I seen for gums problem.