Left Back, Right Back and 1 centre back.
1 DM (assuming Luiz stays). Personally would be tempted to see if we can improve on Barkely for the money he'll cost, but will give him a few more weeks to get back up to speed.
1 striker
1 (fast) winger.
If we get European football of some sort next season and we will also be in a really good position to have good cup runs and we want to push on up the league, there is going to be plenty of playing time for a squad at the level or above our current first team. But don't expect this to happen in one window.