John Gill was an amazingly prolific writer.
It's hard to pick between:
A Complete Body of Doctrinal and Practical Divinity (volume 1) (volume 2) (volume 3) or (abridged)
John Gill's Exposition of the Entire Bible (link1) (link 2)
I'll confess to not having read through either of those, even in the abridged form, though I've read much of Gill's exposition as the occasion warranted.