Arsenal 2nd Season january

[secreteye12]

im in january in my second season with arsenal and i have a budget of 40.8 milllion pounds. i play a 4231 with 2 cm's. who should i buy and sell? here is my squad 4 help:
GK:
Mandanda
Szczesny

Defenders:
Vertonghen
Vermaelen
Schwaab(loan)
Astori
Sagna
Cissokho
Santos
Barzagli(loan)
Alex Sandro

Midfielders:
Song
Arteta
Ramsey
Chamberlain
Eriksen
Gervinho
Wilshere
Gaitan

Strikers:
Van Persie
Walcott
Leandro
Fierro