Okay I think i get if you eat right then everything is balanced and you get enough vitamins, minerals, antioxidants and stuff.
Correct.
There's even epidemiological studies that show supplementing stuff like vitamin C actually slightly increases mortality.
Eat real foods. Only thing you might want to supplement is vitamin D if you don't get outside much in the sun and during winter if you don't live in the tropics, and fish oil if you don't have access to grass fed meats.