I normally go for someone like Palombo to add steal to the midfield. Guardado is always a good get as well.
Get Fazio for central defence.
And I always, always, go for Dario Srna for RB (Richards is really not worth his place in that position)
Lots of striker options to look out for, from Peter Crouch to Aguero.
KEY TIP: in second season, if you have done well in your first at least, Messi is available for 37million or so.
You can't actually get whomever you want as has been suggested, as getting top players routinely cost more than 25million, so its important to sort out the defence and midfield at Man City.
Good luck