Personally I do a modified version of push, pull, legs (PPL) which basically is like day 1: Push exercises (chest, shoulders, tris), day 2: Pull exercises (back & bis), day 3: legs (this one ain't need explaining) where you just add some ab workout stuff on the less busy days (day 2 and/or 3 are best for this). This isn't quite all within a week as after the 3 days there's a rest day so it's a 4 day split which ends up being 8 days, but it works for me and is quite popular.
Man I'm far from serious with my diet, I just had burger king for lunch. I mean just try and eat somewhat healthy but in larger volume. Protein really is the key for it, if there were any macronutrients you'd want to track it would be that and your overall caloric intake since everything else will just fall into place normally. The whole key to gaining weight anyways is the slight caloric surplus (you can only gain if you're consuming more than your maintenance level but only slightly over to minimize fat gain) and then progressive overload with your training.