Doing this stuff on yourself at home is pretty much an equivalent of trying to tune up your car's engine by randomly smacking it with a hammer while being blindfolded. You probably will not break it completely, but it's also very unlikely that it's possible to improve something without understanding how it works first...

Putting aside the fact that a lot of progress in history (herbs and medicines) have been found exactly this way, through trial and error and some 'mystic' guess work.

I don't think we are close to understanding the brain either.

And a lot more and focused progress have been made by people that study the subjects extensively, and try "things" and scientifically measure the impact.