First off, there’s nothing wrong with asking what gifts your guides, ancestors, spirits, or the Fair Folk would like; if you regularly commune with and tune into them, you may be surprised by what they would like to receive from you. Their reality is not our reality- a small thing by our standards can be highly cherished by them. (Say a spoonful of ground chili or honey.)
Likewise, our preconceptions about what offerings should be may be ignored. (While the Fair Folk may like your herbs or burned items, your grandfather ancestor may dislike them and love some beer or tobacco instead.) Garden spirits often will specifically ask for things they don’t already have in the yard- like milk or baked goods. Likewise specific deities if they are being worked with.
So if you have strong feelings about what offerings should be you may need to balance them with what the unseen actually want. You may find yourself having relationships with new entities as a result.
That said, I did try to offer vegetables, fruits, nuts, flowers from my garden (when I had one), or from farmers markets (when I had easy access to them). I generally don’t offer items from our working forest. (I’m trying to get more diverse plants to grow- though bay does smell wonderful when burned. Too bad there is an exotic invasive insect that is killing all of the bay trees here in the southeast US.) I don’t throw non-native seeds into the forest- there are enough invasive non-native plants around already.
Herbs you grow can be great offerings, both burned and otherwise. In the past I made offerings of allowing certain native flowers to grow (on a couple of acres, of a type that everyone cuts down due to the spiny seedpods that get caught in everything), planting natives, etc. I find that the spirits like alcohol, but this may not be your experience. I’ve hung bells, chimes, and prayer flags, and planted various trees/plants as offerings.
Thoughts on offerings in the wild
I usually pick up and remove trash from wild areas that I’ve ‘adopted’, where I go to meditate, or have a ritual. I started out leaving food and drink as offerings with minimal degradable containers. (And items that both the spirits and animals would like.) I tend to only put out food I know will be eaten and/or go back out to remove any rotting food. (If you do this you’ll get a good idea of what foods will cause minimal impact for your area.)
Lately, I’m tending more towards offerings that won’t just rot and go to waste- like native seeds and incense. When we leave this property behind and go traveling I’ll have to put out fewer persistent offerings.
[Note: putting food offerings outside can be ill-advised in many areas. As an example, people leaving food offerings at the volcanoes in Hawaii are causing real problems with rotting and vermin, in addition to possibly being inauthentic and insulting to local religious practice.]
Offerings of earth
Planting trees, herbs, and other plants work as earth offerings. This can include allowing some native plants to grow on your place, or planting natives. (Like oaks.) Items of worth can be buried. Stones or minerals, when rescued from building or dump sites, can be used as earth offerings. (In the California foothills I freed several large quartz rocks from being buried at a construction site and placed them in my yard for the plant spirits.)
Offerings of air
Chimes, bells, prayer flags, windsocks, incense, and herbs can be used for offerings in the wind. I used to have a chime or bell at each quarter outside. Prayers or poems can be written on a thick paper wind ‘sail’ attached to a bell clapper- this way your intent goes out with the ringing of the bell with each gust of wind . (A very nice Japanese custom I have adopted, but I use my own poems now.)
Offerings of fire
Even when I lived in dry fire-prone California, I offered candles outside using very sturdy enclosed lanterns. (On a large stepping stone, surrounded by damp vegetation, next to the house, on a still day, watching it…) LED candles can be used in windy conditions or in situations where an open flame isn’t advised. (My apologies in advance to candle purists.) Burning herbs (especially those you grow), carefully collected resins, seed pods and the like are great offerings.
Offerings of water
Libations can be poured, water added from other (sacred) rivers or wells, flowers strewn, or jewelry or other offerings left in water. I have regular water places I leave offerings at. Adding a small water feature or fountain to your garden for the spirits will be greatly appreciated. This can be as simple as putting out saucers or bowls to collect rain or irrigation water. And the frogs will love you!
Offerings of spirit
Words or prayers of gratitude, positive oath keeping, regular spiritual practice, service to your spiritual community (like volunteering at festivals or gatherings), art, music, and poetry are ways to offer gifts of spirit. I believe a meditation practice also acts as an offering of spirit. So can financial support of your spiritual community. Think about where your spirit ‘lives’ and how you can contribute- you’ll find more ways to give back.