I'd say Bastokan/Republic Knucks or Lynx Baghnakhs. It's really your call, Lynx Baghnaks don't have the acc or atk but are much faster than the Bastokan/Republic Knucks.

I'd say the Bastokan/Repbulic Knucks are bette rthan Metal Knucks. The DMG may be higher but they are also slower and lack the Atk+3. B/R Knucks will do better DoT..

Beyond B/R and Lynx you will probably keep whichever you pick until 32 if you decide to get Impact Knucks which are a good choice.