I'd say get any finisher. You'll have to read up a bit to see what suits your preferences most. You can spend a lot of money on an exotic or just a little on a barber hone. Chrome ox or diamond will work to refresh an edge, but at some point you'll need to go to a hone, so personally I prefer just hones and no pastes.

Personally, I've had a couple different Swaty's, a few coticules, a C12k, an Asagi, and a vintage Thuringian. Initially, I liked the coti over the Swaty's, then I got the C12k and liked that more, then I got the Asagi and that become my go to. The Thurry is recent, and I've not played with her enough to really compare to the Asagi, but it's looking like it'll be the Thurry for Sheffield blades and the Asagi for everything else. In short, my point is there are lots of finishers out there, and the only way to really see what you like is to try bunches of them. For that reason, my advice is start cheap and, if possible, through meets or whatever, try to use other, more expensive finishers before you actually buy them.