A lot depends on your body and its preferences, so I wouldn't recommend anything specific yet. Nail down "what's healthy for you" before you aim to gain weight.

A lot depends on your body and its preferences, so I wouldn't recommend anything specific yet. Nail down "what's healthy for you" before you aim to gain weight. If you can find the right diet, you can just eat more of it and add protein shakes[1], and you'll probably gain. But if it's the wrong diet, you can ignore its problems at a low level of consumption and function in daily life, but eating more will just make you feel ill, sleep poorly, etc. and amplify whatever was wrong with it in the first place. So figure out what you can eat a lot of easily, and what makes you sick. I did not gain until I did this. [1] Again, a lot depends on what blend you're working with. Some are really bare-bones and use only one type of protein, others are heavily fortified meal replacements with a mix of different protein sources.