Michael Pollan's _How to Change Your Mind_ has a good overview of the attempted scientific research. Early research was tainted by overzealous experimenters, then research was banned for a long time, and recent studies have only been approved for serious conditions, like treatment-resistant depression.
The real problem is that creativity, the long-term generation of valuable ideas, is basically un-measurable. Scientific studies of "creativity" exist, but they all pull the ol' research switcheroo by measuring something easy to measure, rather than the kind of creativity that matters.
So, don't expect good scientific evidence of improved creativity, from any treatment, ever. That's as true for substances as for, say, whether to write on paper or at a computer. Most novelists swear by one or the other, but there's no feasible scientific study you can do to decide which produces objectively better novels. Same for whether meditation improves creativity.
(If you want to get into this line of research, start with meditation rather than psychedelics. It's much easier to get approved.)
For making your own plans about how to maximize your mental output, all you can really do is ask people whose works impresses you (and who are willing to talk about such things) what works for them, and then try those things to see if they work for you too. Being careful to compare the results side-by-side some time later, to reduce bias.
LSD is ... frankly, in my experience, a lot of bullshit. I've done enough of it in my youth to early adulthood to be annoyed I wasted those brain cells instead of thinking about interesting problems. I've also never seen anyone who it improved; mostly it seemed to increase people's self-regard.
Put it another way, invention and new ideas haven't exactly increased since Albert Hoffman's big idea. You'd expect there to be a lot more cool stuff if this were really true, as there are certainly a whole lot of people who have tripped balls in the last 50-60 years.
People used to think sniffing ether, taking absinthe or breathing nitrous was incredibly profound. Until enough people did it that the evidence was underwhelming.