I recently read SPQR: A History of Rome by Mary Beard. It got me interested in reading more about Rome. I also listened to the Hardcore History episode about The Gallic Wars, so I'm interested specifically in that topic.
Would a modern reader get anything out of reading Caesar's actual commentaries, or is it too difficult without a historian guiding you through the context to actually get something out of it?
You can sort-of compromise by reading the Landmark edition
This includes maps etc. which might help you follow the action.
They also published a bunch of appendices/annexes/essays online (previous books just included these in the print version, but by making them online a side-effect is they're free)
If you go with the secondary source option, I'd consider Caesar, by Adrian Goldsworthy (haven't actually read it, but have read lots of others by him and they're great, and reviews of it draw attention to the Gallic Wars analysis being great as the writer is a military historian