What do I offer to a demon that ive called on (so far Seere and Dantalion) but I only feel their presence, I don’t physically see them…and then find that they are working on what I wanted but we never agreed to any offering or agreement with the spirit?
You don’t really need to give offerings but if you feel you must, a genuine thank you, and maybe a glass of nice red wine would be sufficient.
Give them things from your heart, give them whatever you feel like.
I agree with @Razuna as well. Spirits of all sorts seem to really appreciate personal art dedicated to them, so draw them a picture or write a poem and read it to them. It doesn’t have to be good, it just has to be heartfelt.