I used the ginger shampoo for a while and at first it worked, but then it just got worse and then my derm officially diagnosed me with seborrheic dermatitis which is just a fancy way of saying severe irritation and flakiness on the scalp. So yeah, I would definitely get it checked out professionally first to rule out any actual conditions because any of the 'drugstore' brand shampoos and products probably will end up doing more harm than good if it's an actual condition and not just a bit of dandruff.
If you try Nizoral, make sure you use quite a bit and really focus it only on your scalp and then leave it for 5 mins or so before rinsing (I usually shave my legs during this time haha). For a medicated shampoo, it's actually not too stripping. I wash my hair twice a week and use it both times but follow up with conditioner for sure - just avoid your scalp with conditioner & products. Once every 2 weeks I use a clarifying shampoo (I use the neutrogena one) instead of nizoral to get rid of build up which I find also helps.