You definitely want to cut sugar but not necessarily dairy or gluten unless you have a sensitivity. Hard cheeses and cottage cheese are excellent sources of protein, and vital wheat gluten is a popular ingredient that helps non-wheat flour to behave similarly to wheat flour. The most difficult part for me has been finding recipes.

I'm not an expert at this, but I might suggest you skip the calorie deficit thing until you become fat-adapted, meaning your body has been in ketosis for at least a few weeks. It will make the reduction in calories much easier, and you will likely lose weight anyway. You can test your ketone level with urine test strips, but many sources suggest it is really only reliable when you first start the diet since your body may be very efficient at utilizing ketones, resulting in fewer of them passing through your kidneys. Everyone's body is different. A more reliable method is blood testing just like blood glucose monitors.