There’s a lot of good ideas in How do you expand your knowledge of different taxa?.
If you can check with a local plant, insect, bird, etc. group, they might suggest a good local resource. For example, in my area, these are very good. I only learned about the 3rd one from a local CNPS meeting in the last two weeks:
- Wildflowers of Orange County and the Santa Ana Mountains
- Flora of the Santa Ana River and Environs
- Wildflowers and Important Plants of the Inland Empire
Since reading the above thread, I’ve also started looking at daily research grade observations in my area. This is a good way to learn new ones too.