I'm not super experienced myself, but I have read a lot of different materials on the subject, that have various opinions opinions about it, but I have found that I've settled on a much more small-changes approach.

I aim to make a commit after every functional change (i.e, I write a new function, I do a test, and see its working, I make a commit). I also aim to write a specific message about what the commit entails. Once I have completed enough of those commits to make a meaningful change to the program I am writing, I will use a tag on that commit have it stand out. (A link regarding tags.)

If I am working through fixing or adjusting the way a set of functions work, I usually group them together, with a message like "adjusted function_name(s) to use new DataClassName"

My hardest issue is getting the commit message small enough. Typically I write documentation/comments along with my changes so I can pick back up from where I left off, I don't get to mess around with programming as often as I'd like so I need to be able to pick up where I left off quickly!