Some offerings can be considered universal, for example, quality time. I know, I keep repeating this one, but it is often looked over, yet it is one of the most potent of them all. You don't need expensive tools or even luxurious altars to please a deity. You can, of course, go for it, but it will not separate you from those who lack of wealth, but not dedication and genuine respect.
Your time is precious, just like your energy, and if you focus your attention and emotion on them, this will appease them, while energetically charge. You can't really go wrong with this one.
ㅤReading of them, talking about them, writing about them, crafting, creating something dedicated to them (be it an artwork like a novel or a drawing, a painting), but even cooking and offering it is a way to gain their 'favor'.
ㅤYou can also go out and do something they are familiar with. If a deity is connected to forests, and you have one to visit, feel free to turn this time, while having this deity in your mind. If one's familiar with flowers, feel free to spend some time gardening outside in their name, or for their joy, in their favor. Go creative, don't be afraid. Watching a movie connected to the deity is also an act that'll profit both of you, if you watch it in the right mindset, offering this act for them.
I think, it is essential to have a pure intent, without ill will and that whatever you offer is genuine. It'll show on your connection and ultimately, even on the results. This applies on both 'quality time' actions or other offerings.
Whether you know a deity already or not, you can always ask them what would they enjoy in that given moment, or you can do your research, if communication is a no go for you for whatever reasons.
ㅤFor example, I know how Belial is always pleased with alcohol offerings, and he loves chocolate too. He prefers sharing; wanting me to consume my offerings what he accepted, creating a form of energy exchange, while also just sharing our private moments together this way. Sitri is really enjoying sexual energy offerings. Paimon loves art and poetry, so creating something for him would be definitely a good way to go. These are just few examples. Sometimes a deity crosses my mind, and I end up sharing the meal I just prepared, not specifically for them, but I pay respect towards them by allowing them in my everyday life, and giving them access to my regular resources, out of love and respect.
Of course, you can meditate on them, channel their sigil, astral project to their realm, or do other magical practices dedicated to them, involving them.