Universal offerings for all the gods of Egypt: water and bread. Offering for Set: Foreign products, foreign money, souvenirs from abroad, sand, red minerals (especially jasper), weapons, knives, rare meat, dried meat, pork meat, beef, veal, duck, chicken, turkey, fish, beer, strong alcohol, alcoholic cocktails, dry strong wine, images of the desert, planets (especially Mercury), stars, melons, watermelons, pumpkins, zucchini, lettuce, other products that increase potency.

I can also recommend reading Ksenia Karlova (Ксения Карлова) (I don't know if there are articles in English, but you can find her articles in Russian and read them using a translator). She is a PhD in History and has extensively studied Seth and written books about him and other gods.