Assuming you want what most view as a mainstream blues sound, a small Fender tube amp. You can also try something like this in front of your current amp:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Actually works pretty well for getting a Fender tube sound out of a clean rig and if you don't like it, you can send it back.
As for me, I like a clean archtop sound for blues. Scooped out mids and as rich and acoustic as the guitar and amp will produce.