Give me some diet tips

I could really use some diet tips because I hate when they call me names. I am really skinny and I had so many problems with it that I cannot stress out how bad it is for me. But I cannot seem to put on any weight. I know that a pretty simple solution is to eat everything and eat a lot. On the other hand though, I do not want to get fat. I would love to be well built but I am aware of the fact that it is a really hard and long process. I am really sick of being so small. People think that I am feeble because of my size and thus, I have huge difficulties in finding a real job. I mean, no one really treats me as they would treat someone in the same age but in normal size. That is quite sad, if you ask me. That is why I want some diet tips I really want them. I need help because I cannot go through it alone. I mean, I tried eating a lot before but I must digest the food too fast or something like that because it does not help. I need diet tips because I need to know WHAT to eat to put on weight. You cannot eat anything. I want to eat healthy stuff while still being able to put on additional pounds to look better and more serious. I am twenty-four years old and I am so lanky that I look like a teenager. It has to change! I need help!