I also have very fine hair. It really likes the more natural products. I went from being a winter wavy/3a summer to a winter of the curls in my signature picture as a result. The turning point was starting to use soap bars to cleanse after 6 months of cowashing. It tightened curls and added volume. My most commonly used products, like the others, are in my signature.
3a (Corkicelli), highlighted, fine, low porosity

HGs: Anything Sevi; Curly Kinks Satin Roots, Curlycue ReNew and Coil Jam; homemade FSG and okra gel; soap bars; UFD Curly Magic; Botanical Spirits Jellies, CJ Repair Me, Aloe Fix