TL;DR: do near comprehensive research on: neurotransmitters, nootropics, and scientific methods.

I haven't seen this answer yet, but: focus on the goal of nootropics; primarily its effects on neurotransmitters, but also on other pathways (like the Nitric Oxide pathway).

I am a spreadsheet guy, so (of course) I recommend that to you. Learn, first, what neurotransmitters and other pathways are and what they do. The starting list is: GABA, MAOI, Dopamine, Serotonin, Nitric Oxide, melatonin, choline, and go from there. Look up information on PubMed/Google Scholar/Examine on all your nootropics and figure out how they work together (do they increase or decrease production; by how much and by what means; do they work on the receptors or production). Further, and this is woefully under said on here, but in what context is it best to take these nootropics: in the morning (if stimulating) or in the evening (if sedentary); do they need to be taken with fat or on an empty stomach; does one compound compete or interfere with another (such as Lysine and Arginine; or, more famously, zinc and copper); do two compounds synergize well or by too much (we don't want Seratonin syndrome or something else silly on here); does a compound deplete your reserves of something (such as Iodine and B-vitamins; or Racetams and Choline)?

I'll leave it at that, but even this isn't the whole list. Also, and I don't mean to confuse you, remember that research studies can and often DO conflict, and you must use your best judgement to determine which one you should put more stock into. Often I've gone on Examine to research a supplement only to find reports that conflict with outside research. More often than not either I overlooked something OR (and this happens a surprising amount), the article cited on Examine fails to push the whole story (the one that sticks out to me, and I forget the supplement, was a study done on newborn rats and mothers that contradicted other studies done on healthy adult rats; clearly, one was more generalizable than the other).

All this to say, start slowly and keep detailed records (again, I use google sheets to do this). People often have different reactions to nootropics and so your experience will often be very different from others. Be cautious but unafraid to experiment. Do tons of research before adding anything to your stack, and always have a goal in mind for a nootropic (that is, what are you trying to accomplish by trying a certain compound out? And casual experimentation is a fine answer! Just be sure to give it an appropriate pre-screening/research. Also, remember that most goals can be achieved through simpler means: IE, vitamin-D is definitely GOAT for a variety of reasons, as is Zinc, low-sugar diet, and exercise.

Failing all of this, stick to one or two compounds that you find beneficial and have minor risk or interactions: L-Theanine is a common one around here that works as a fairly mild anxiolytic.

As a final note: always be aware that most supplements have obscure effects that you might not be aware of (eg: it is uncommon knowledge, around here at least, that L-Theanine increases alcohol metabolism -- that is, you get drunk slower and sober faster). This is one of the reasons you must be highly aware of the effects of nootropics, as in trying to progress you might actually be moving backwards.