Because the game keeps changing, there is no way to have a truly perfect diet, or a truly perfect life. It’s a moving target, which means you have to keep adjusting your aim. The way to keep making your diet (as well as your life) better is to do more stuff that makes you feel good in the long run and do less stuff that makes you feel bad in the long run.
If you can’t tell what makes you feel good and what makes you feel bad, keep a journal and track what you eat, what you do, and how you feel. Look for patterns. Do you have more or less energy? Are you happier or sadder? Is life better or worse?
It is always a good idea to consult with a trusted medical doctor and tell her what you have in mind, and what you’re trying to accomplish.
If you can only do one thing to get closer to what you want to achieve health-wise, I’d say cut down or eliminate added sugar to your diet. Here’s a great list of how sugar is ruining your health (references are at the bottom).