I’ve had psoriasis since I was 14 (now 35).
It was so bad when I was younger it practically covered my legs, elbows and scalp. 
I used Dovebet/steroids on and off for years and while it reduced the area that is annoying you at the moment, it can’t be used either any kind of longevity. I ended up playing whack-a-mole with my body because as one bit went down it would appear somewhere else.
The best medicated treatments I’ve found:
Capasal shampoo - for scalp
MG217 coal tar formula - the one that is truly disgusting with a texture like Vaseline. But it really, really does work.
Antihistamine- I used to take them every day, and this was really when I started to see the first reduction in angriness and flakiness.
Best non-medicated treatments:
Hands down, without a doubt, sunshine.
Having an awareness of your stress level and doing something about it. It does get worse with stress (I find).
Having an awareness of triggers or allergies and doing something about it. For example, whenever I drink cheap beer, my psoriasis flares. When I drink a ‘pure’ spirit like gin or vodka with tonic, it doesn’t. I used to eat a lot of cheese, dairy, yoghurt (which it transpires I’m allergic to) and actually cutting those out has made a huge difference. Not at all suggesting you do FODMAP or anything but, I think we all know when we feel bloated or our gums itch or have a poorly tummy, just listening a bit more to your body can really help.
Use a natural soap - I’ve been using goats milk, but I’ve found sodium laureath sulphate based products (for me) cause irritation. Cutting them out made a huge difference.
Absolutely do not: use Aqueous cream on wet skin. Whatever any doctor tells you, it’s a lie, you will end up feeling like you want to rip your skin off.