The best diet is delicious. That's rule #1

But generally I would say try to have balanced variety within a finite predefined standard deviation. Try not to go to exotic unless it's necessary.

If your vegan all these rules can apply to you also. Like for example vegans be ontop of nightly soaked chia seeds. Go heavy on the nutrional yeast and try to look at successful cultures that have enjoyed delious food while being vegetarian/vegan. Like the southern indian subcontinent or the true Jamican rasta's for example. Just a quick list of things vegans will find beneficial is purple seamoss, Chinese ginsing, himalayan shilajit, and eating sprouts like bean sprouts. Also iv pinpointed the most heavily weighted metric of health is the ability to sustains one own mental well being such as a positive outlook on future outcomes and feeling in control of your destiny.