Fruit sugars, honey, anything with omega acids (both of them) = brain food. Green/black tea is good for focus, so is guarana.
IME, the most important thing is not to overdo things. Something may be healthy but if you use it too much, you won't get good results from it.
Balanced meals are the way to go.
Apart from diet, regular everyday exercise that keeps the blood pumping will help you the most, it wakes you up, oxygenates the system and helps redistribute the nutrients. When the whole body is healthy and happy, you get more efficiency with everything, cuz the body is a self-supporting system.
And I can't really help you with recipes cuz I make my own recipes based on what I've got at home at any given time.
Would have never discovered pancakes with tartar and honey otherwise

Ofc, don't make it an abrupt shift, no need to shock yourself. Take it easy but take one decisive small step, every day.