I did few diets (“full” organic/natural, no carbs, fasting, calories deficit) and I think best way to eat is eat balanced foods focusing on proteins , have some time between meals (snacks are okay, but dont overdo it) and before sleep so your stomach get some rest and throught the night you can fast a bit.
If you wanna lose weight, just eat less, focus on less carbs and move more – maybe change training plan (more sets and reps or add cardio), take walk instead of bus, take stairs instead of elevator etc. If you wanna gain weight do oposite.
Also keep your diet simple and dont do some hardcore stuff, because it may be too much for you and you can fail (which kinda happen to me nowdays) and supplements like vitamins, minerals and joint/bone/tendon supplements are fine if you need them, but if you eating balanced food you should have almost everything. And of course go for less processed and more organic 🙂