Gaining

Right now im 120 pounds i used to be 110 but after about a year I got to 120 Im not sure what a good goal weight would be I just want to be more squishy and what not. recently I've tried Stuffing my self I try to eat about 600-900 calories at the end of if the day. But I don't know what's heathy or a heathy rate. The main thing is I for sure do not want stretch marks so I want to gain as fast as posable with out stretch marks.

Everyone’s body reacts differently. Personally I get stretch marks even if I gain quite slowly, but there’s others who can gain a lot faster than that without getting them for quite a while. If you got stretch marks just from getting taller/your body maturing like I did, it’ll probably have to be pretty slow if that’s a dealbreaker for you. If you didn’t, you’re probably safe to gain 5 lbs a month or so, maybe with some rest periods between pushes to let your skin catch up.

generally 1-2 pounds a week is considered safe afaik, which def adds up quicker than you'd think at first