I have been on it for three years. I just had a pill cam and a colonoscopy. Doc said both were perfect. In fact he has taken all reference to Crohn's off my chart. You could say SCD cured my Crohn's, well sort of.
Here are a few things I have learned. In the beginning eat absolutely nothing from a can. There are a few things that we can eat from a can on SCD, but you should only eat food prepared by you. Trust nothing. You need to assume everything you are about to put in your mouth is illegal, unless you know for sure it is legal. I did not do this (dried cranberries, melatonin, sweet n low, a few others that I forget), the diet did nothing for me for the first 8 months.
Start with the intro diet. When you are ready, add foods slowly. There are phases on pecanbread.com that are not part of the diet, but I find to be very useful. They are worth considering but not required. After 3 years I still do not eat phase four foods. I learned the hard way that going to fast is not worth it.
I find bone broths to be very healing. Consider buying Nourishing Traditions by Sally Fallon.
Make food you love, use kitchen gadgets (food processor, crock pot, immersion blender, big pots,..) make lots of it and freeze.
There is no single answer re what to eat. You are trying to gain weight. I would avoid nut flours for now.Too advanced for a newbie. Add more healthy fat, pastured meat, coconut oil. Make yogurt out of cream and make ice cream, or ranch dressing. Add butter to well cooked and de seeded veg. Be careful of too much honey and nut butters. They are high calorie but they can be tough on lots of folks. I ate too much of that also and it was only after I went low carb that SCD worked for me.
Almost 100% of new SCD folks eat too many sweets the first time they prepare them. For me it was almond butter cups. Made with cocoa butter (it is amazing), my preferred organic honey and crunchy almond butter. Tastes amazing but after I ate 1 lb in one sitting I was sick for 5 days. This happen to most, but I hope you are stronger and smarter than me.
Join SCD yahoo support group. This is where the real experts are.
Few people are in a position to take this on, but for those who do, the success rate is amazing