Food staples and some questions

What are your standby staple foods? How many meals do you have a day? How do you guys handle ice cream/frozen greek yogurt, sushi, and fruit juices? Do any of you turn to processed food when it gets really bad so you can keep your calories up?

I've half-heartedly followed the GP diet guidelines in the past but now I'm making a serious effort because I'm at a really low weight and need to gain. I was doing three meals but now I'm going to switch to four. I've read about people including ice cream because it's easy to eat and provides a good whack of cals, even though it's not the healthiest stuff. Sushi (philadelphia rolls) seems healthy, just rice, cream cheese, and salmon, but I didn't know if it would be a problem or not. I've had it but it was when I was doing bad, it didn't make me worse so that was good but still couldn't judge the full effects of it.