I think all we really need in the summer is:
Top priority has to be one more top striker/forward. We've been extremely lucky that out front three have been relatively injury free this season.
A good CB to give cover, along with Matip, for Joe and VVD, De Ligt would be absolutely perfect, if possible, but if not then how about someone like Tarkowski.
Need a full back who could cover both left and rght flanks, but especially Left.
On top of that possibly a good utility midfielder to replace Milner, although Grujic can probably fill that role.
As for GK, surely one of the youngsters can step up if Migs and Karius move on, otherwise just get a good backup keeper.
So that's it, we should have plenty of money to get those players, the only one which should cost any big money would be Striker, the other positions are more good back up players, in the way Shaquiri was this season, at least first half.