Phenibut or melatonin but don't mix either of those with alcohol
there are some questions that nootropics simply arent the answer to. once you get into any sort of depth with meditation youll quickly see that any sort of substance taken is most likely counter productive to achieving the end result. perhaps if you had say adhd, there could be certain drugs to take to reduce the fidgety-ness that could help you early on to learn the practice and technique, but eventually even that would go out the window
Just google breathing meditation. That would be the most common one. But there are different types also. But Starting with that would be my recommendation as its fairly easy to start with and most people doing mediation regulary can aid if you need help with the practice.
I do it to everyday out of habit nowadays. Like brushing my teeth. And it makes me remeber that everything is ok.
The idea of taking a substance to improvemeditation, while not totally as strange as it sounds, really isn't the best idea, given the goal of most meditative practices, such as mindfulness.