My favorite one is Coluracetam.  
This powerful neurotransmitter is central to several cognitive functions including focus, motivation, learning, and memory. The supplement is particularly effective in regions of the brain that control sight (vision) processing. More other stuff you can read here: https://nootropicboost.com/buy-best-nootropics/coluracetam/ is it dangerous? I think even chocolate can be dangerous if you eat it too much. You need to know the measure. And everything is going to be OK.