If it's subtle or really complicated, a journal and making one and only one change at a time are enormously helpful "best practices" for self experimentation.
But for the assertion here that "ketogenic diet helps with schizophrenia," neither a ketogenic diet nor schizophrenia are subtle things.
And that last tip of separate things by X hours? That's actually a generally useful thing that applies to a number of things.
Calcium and iron interfere with each other, which is likely why a kosher diet has edicts against consuming beef and (I think) cheese/milk products together in the same diet. I try to separate them by at least 30 minutes, especially if I am specifically trying to treat anemia or a need for calcium. (But I generally try to separate them because consuming them together amounts to wasting the nutritional resources they represent.)
Zithromax (plus related drugs, I think) and magnesium are supposed to be consumed separately. They use the same attachment sites on a cell and actively interfere with each other's absorption. So consuming them together means you don't get the magnesium you need and you are undermining the effectiveness of the drug you are on.
In the opposite direction, some things need to be consumed together for best effect. This is the principle advocated for in the book Diet for a Small Planet that promotes protein complementarity as a means for vegetarians to get enough protein.
In later writing, she says she regrets making it sound so challenging. Most historically vegetarian ethnic diets already use ingredients in the appropriate ratios, so many traditional dishes already fit the model she advocates for.
The book also has a few really excellent recipes in it, so it's worth having even if you skip the first half of the book which is a political work outlining how beef contributes to civil war and starvation globally and proving that all countries, even poor countries, can feed their people on traditional locally sourced diets. What we can't do is sell imported beef to peasants and expect them to be able to afford it as a staple and a lot of starvation is due to war (often civil war) cutting people off from food access.
It's more complicated than that and if you want a stronger argument for promoting vegetarianism as the practical choice for reducing some of the problems in this world, it's got some excellent information in it, better than a lot of the BS scare tactics and high-handed moralizing that is all too common. But you can just flip to the back of the book and look up Complementary Pie (a bean and rice quiche dish) or Mjeddra and happily go to town cooking.