What is the best treatment for psoariasis?

Many. Your dermatologist can help you here. Treatment includes sunshine with skin protection for the risk of skin cancer, light therapy, topical medications including corticosteroids, topical tars, other topical medications, oral medications and even injectable and infusion medications inclduing biologic therapy.
Cortisone creams. Psoriasis is common and sometimes runs in families, it be very minimal, with just a few patches, thick nails, or dandruff, or it can be very severe with thick red areas on the scalp, and other parts of the skin.If it is mild, you can try a Hydrocortisone cream, moisturizers and sun exposure until you tan. If it is very severe, than you need to a dermatologist for prescription medicines.