For me we absolutely need some physicality in midfield in front of the defence. Somebody in the mould of Zakaria/Kondogbia, to line up alongside one of McGinn or Luiz instead of using them both. After that, pace out wide would be my next priority, followed by a number 10/tricky type who is comfortable on the ball and in possession in tight areas to alleviate some of the pressure off Jack. Buendia is often touted and I think he'd be ideal, although not sure how much he'd cost now that Norwich are on their way back up.
In terms of pacey wide players, I think we could do worse than look at clubs just outside of that top European bracket, like the top 3 in Portugal or Lyon/Monchengladbach etc type of clubs. We could probably offer decent, competitive wages to their kinds of players with a 3rd successive year of prem money further alleviating FFP constraints.