I've always felt a little shaky when giving sacrifices to the gods. (Hellene, BTW.)
I prefer to use things from nature or things I have at home since I don't have the money to buy any special supplies unless they are real cheap. I'd rather give something from my heart rather than "money".
I'm not exactly sure how to give a sacrifice. In my own way, I use my gift of poetry and writing oftentimes. Writing poetry or short stories based on certain myths about the god and offer it up to them. But if I can't write that day, what would be a good sacrifice to give? (Note: can't do food. My mom is not used to my beliefs.)
How about pouring a libation outside? It's very traditional in your religion, it wouldn't be something left out to make your mom uncomfortable, and it doesn't have to be expensive. I used to offer sparkling grape juice as a replacement for wine when I lived at home and was under 21. Honey, juice, oil (like olive or almond), milk, or tea would be very easy to get and only cost a few dollars.