I wanted to know the "best" foods to feed 1 year old for most quick possible weight gain.Maybe possible additives?

How much does the baby weigh?
Is it a boy or a girl?
Why are you concerned about QUICK weight gain?

My daughter is 14 months old and just over 16 lbs. dr. said if I can't make her gain at least 1 lb. in 1 month they want to admit her and insert a tube into her stomach to force on weight

I would guess some of the baby cereals would be good for weight gain. If she has some type of problem preventing her from gaining weight normally though I would guess it may be more complicated than *fatting* her up with food.
I would watch the baby cereal too though especially if it contains iron because it can constipate.