For HH I can strongly recommend any aluminium-based antiperspirant. They work.
In the first weeks and months I had to apply them at least 2 times a week, after like half a year every 5-7 days, and now it's enough to apply it every 9-10 days.
Totally worth it. Like 15 Euro for a little bottle, but one lasts for over a year or so.
As for Niacin, I just read a bit about it. Niacin = Vitamin B3. If you're not a vegan/vegetarian I wouldn't recommend taking it.
Plenty of Niacin in fish and meat. Taking too much over a long period of time can lead to many potential negativ side effects, says Dr. google.
If I wasn't into powerlifting/bodybuilding, I never would've started taking any suppplements whatsoever, hell, I guess I still wouldn't have heard the term "supplements" until today.
My standard stack is:
-magnesium
-zinc
-5htp
-3 grams EPA/DHA combined (10 grams of fishoil)
For when feeling a bit ill/having alot of stress/having <6 hours of sleep for several days a week:
-multivitamin
-vitamin C
-OPC
I eat 500 -700 grams of vegetables and 150-200 grams of fruits a day anyway, but one can't literally have too much vitamin C when being on the edge of getting a cold etc.
Also, 5htp definitely has improved my sleep alot. Altough Dr. google says taking supplements that convert into melatonin/serotonin for too long can cause brain damage ... not sure how long I should take it before taking a longer break from it.