it looks like your pretty set in the midfield, so i'd look at buying a young back-up keeper that could possibly takeover from Gomes in the next season, so i'd have a look at the following: Sergio Asenjo, Vincenzo Fiorillo or an English keeper in the form of Scott Carson, if you want someone who can instantly make a difference in goal go for Igor Akinfeev, he's a brilliant keeper who makes fantastic saves, he's saved me on countless occasions.
Maybe a young DC, look at mamadou sakho, has great potential and Federico Fazio who is quite good at the start of the game but will get alot better than he is at the start of the game.
And fnally it looks like you might need another striker, so again go for young but good, Bojan sometimes you can get on a free at the end of the first season, Federico Laurito is also a very good striker or if you would prefer to buy a striker in the form of a target man look at Hulk of porto, Oscar Cardozo of Benfica i think and Eugene Seleznyov of Shaktar.
Hope this helped.
