Can they still buy players? After spending incredible money last season. Not to mention that with the salary list of each player, they will need a lot of money. It looks like it could violate FFP rules. This season Barcelona proved a failure for the UCL, with the same player Xavi may need to improve the mentality of the players. Rumours Messi will return, it looks like it could help them in the UCL. But now that won't happen, it looks like Xavi has to look for non-star players with good games and low prices.
Barcelona is still possible to buy players, they seem still have funds for new players. But surely they probably won't target signing top players with high prices, Barcelona looks for good players with cheap prices. Or Barcelona will try to negotiate the players with free agent status. I assume Barcelona will focus on signing defenders (left/right backs) or defensive midfielders.
Yep, Barcelona failed in UCL & Europa League. So, I believe Xavi will do something to build more Barcelona squad. One of the ways is to sign new players who can support the current players to be stronger. Barcelona seems to target winning UCL trophy next season. They must target a more prestigious trophy after they won La Liga trophy this season.