I think Barcelona still should make two transfers to specific areas. These areas are defensive midfield and centre-forward. Because in the defensive midfield there is still only Oriol Romeu. Of course players like de Jong and Kessie can also play there. However their main positions are central midfield so it is better to use them there.
For the other position there is only Lewandowski there. Barcelona don't need to spend so much money for bringing a striker. They can even loan someone who can be useful in Lewandowski's absence. Signing a backup striker should be even the priority for them.
They still have de Jong and Kessie and both played defensive midfield so far and de Jong even played both sides, but do they really have the classic defensive midfield? With de Jong and Gundogan they should be ok although I can also see the need for at least a high quality backup.
I think the exchange between Manchester City and Barcelona where there were rumors about exchanging de Jong for Bernardo Siva won't happen because does Barcelona really need Silva? He is good of course, but currently Barcelona has several offensive players with decent quality. But what I miss is this one star player that is above all else.