Depends on the type of games you play & your budget.
I like 21:9 monitors for immersion so I'd probably go 3440x1440P/100hz+/IPS or VA and Gsync or Freesync (with newest drivers and DisplayPort cable). If you consider 21:9 just be aware there are some AAA games such as Overwatch that don't support it on purpose although other Blizzard games such as Diablo 3 & WoW do. Also even if there isn't 7sufficent 21:9 support more then likely there is a fix online but I would say most games do support 21:9 natively.
If you prefer 16:9 then you could go either 2560x1080P/144hz+ or even 3840x2160/60hz+ although those 100/144hz screens would require you to lower the graphics a bit to get even close to those speeds however a monitor like that could...