Some of the most common signs that a scalp is healthy include: no dandruff, little to no oil production, no inflammation, and Scalp Brightness (a measure of how light or dark the hair is). Most of the time, my scalp is healthy and I have a little dandruff every now and then (generally when I'm stressed out), but it's limited to a couple of flakes here and there. If you want, you can also consider getting a suitable treatment for your hair from https://www.thehairfuel.com/a-how-to-guide-to-scalp-care-for-hair-growth/.
One sign that your scalp is low on oil is dryness. If you are experiencing dry hair, that means that your scalp may lack essential nutrients like vitamin A (which helps your body produce oils) as well as vitamin B-complex (which allows the skin to produce collagen). I typically experience very little if any dryness.
Another sign that your scalp is low in oil is that your hair appears dull. I would say this one is more important than dryness. If you notice your hair looks dull, it's a pretty clear indication that there's not enough oil in your hair to prevent the hair from becoming dry and brittle.I typically cleanse my scalp once or twice a week with my usual cleansing agent and then apply oils, which are comprised of many different nutrients and antioxidants (primarily vitamins).
I use some sort of combination of these treatments on my head as well as on my beard – never neglecting either area. If you want to get a deeper understanding of what are the best oils for healthy, moisturized hair and skin, please check out The Hair Fuel official website I suggest bookmarking this link, because you're likely to find it very useful.