Robinson's a bit rubbish, Cahill and Vermaelen while good are not top-class, and Walcott's poor.
I'd try getting Ochoa, or Akinfeev if you have lots of money. Invest in some good centre-backs, Sakho, Otamendi or Kryvtsov all spring to mind. Get a better striker too, like Giuseppe Rossi or Aguero or Dzeko.