Can't afford to eat right... can't gain weight.

Hi, I'm Mandi.

I am a mother of 2 boys. I am trying to gain atleast 3 lbs. as I am a little under weight... I feel like i'm the only one here with this problem.... Let me know if you struggle with this also? and maybe tips to help? I would like to create a workout that I can tone and gain a bit more muscle.. My arms are good kinda look like men arms lol. Add me I'm new to this!