The best I’ve found for focus is simple caffeine. Amphetamines are good for motivation but give me too much motivation to do things other than what I need to be doing. Methylphenidate is maybe a bit better but still a similar story. They also both have considerably worse side effect profile than caffeine. YMMV though, I am an adhd-coded individual and everyone’s brain chemistry is a bit different anyway. Lion’s mane and/or Cordyceps double extract tincture is not bad but I’ve grown to be weary of neurogenic drugs, although that is more of a personal decision.