I am not an expert at Geometry Nodes, but there are a lot of things you can do with just basic knowledge.
There are loads of free tutorials in you tube, I recommend you start there.
Do be careful not to watch any that are from before the rewrite.
In Blender 3.0 Geometry nodes were completely rewritten and many of the old nodes were discontinued (disappeared) and changed for the concept of “fields”.
You could start here:
Geometry nodes are in continuous development, this means that every update of Blender brings in new nodes and possibilities so I would probably recommend you watch tutorials from 2022.
There are also many threads on this forum that can help you (some more technical than others).
higgsas has done some incredible work with Geometry nodes and is kind enough to share a file with loads of useful node groups, you can download his file and look inside the node groups to see how he has done them. Watch a few tutorials first to understand the basics.
You just have to dive in and start simple (similar to learning Blender in general)
Edit:
I recommended Andrew price to start with because he tends to “hold your hand” but I am very fond of Erindale’s (pretty technical) and Chris P’s (always fun to watch) videos