Your question is so broad that it's hard to answer. There are a million different philosophies about what humans should eat to be healthy. Some people will tell you a plant-based diet is healthiest. Others prefer paleo. A lot of doctors promote the Mediterranean style diet as the healthiest (which the Mayo Clinic describes as "While there is no single definition of the Mediterranean diet, it is typically high in vegetables, fruits, whole grains, beans, nut and seeds, and olive oil." Most of us probably would benefit from limiting intake of processed foods and junk food.
Different bodies react differently, so it may be a matter of trial and error to see what kind of regular diet agrees with you. Personally, I do best with moderately controlled carbs (with very few of the refined, white variety). I'm also a carnivore who needs at least a little meat in my diet. I eat fruit regularly, but I can't overdo it as the sugar in fruit starts to affect me just like the sugar in a candy bar. So I pretty much eat meat, dairy, eggs, veggies, a moderate amount of fruit, nuts, and various kinds of fats. But that's what MY body likes. Your body may prefer vegan or something else entirely. It's really a matter of trying different approaches and seeing what works best. Good luck!