The Italian, who signed a new five-year contract to stay with the Barclays Premier League champions this summer, remains optimistic he can land the players he wants, with the start of the season less than three weeks away.
Mancini said in an interview televised on Sky Sports News: "We need to work harder than last year and buy the players who can help our team. I'm confident.
"We don't need big changes, not 10 players like two or three years ago - but we need three, four, five players. But they can be young guys for the future because it's important to put them in the squad and make them good like the players we already have."
Mancini has previously expressed his admiration for Robin van Persie and it has been confirmed that City are among the clubs to have lodged bids for last season's Premier League top scorer.
However, the Holland international striker has been linked with several other top teams following a 37-goal season with Arsenal.