Chris Coleman is hopeful that he could still make four more additions to his squad this month.
Coleman made his first signing as Sunderland boss earlier this week by bringing Jake Clarke-Salter from Chelsea on a loan deal.
Sunderland's difficult financial situation means he is relying on loans and he will continue to target promising players from the Premier League's top academies.
Sales of players in the current squad could free up some funds but the Black Cats are yet to receive any bids from other clubs.
Nevertheless, Coleman remains optimistic that he can make significant additions, even if it is on a short-term basis.
He said: "We want to bring in new faces but it has to be the right personality coming into the dressing room to help what we've already good. That isn't easy because of course other clubs in a similar situation want to take loan players. It is a dogfight but getting Jake is a good start for us and there's still two, three of four more we'd like to do before the end of the window.
"Immediately you feel here what type of club it is, the difficulty it is in. I think it has had a lot of turnover in terms of player ins and outs, a lot of money has been spent and it hasn't quite worked out. We need to be realistic in where we are, and the reality is at this moment in time we can't spend millions on players, but even if we could the principle would be the same, getting the right personalities."
Coleman has been impressed with Clarke-Salter's youth career so far and he is likely to go straight into contention for the game against Cardiff City on Saturday.
He said: "I'm really happy with Jake. I keep talking about bringing the right kind of person into the club, he's young, hungry, wants to achieve, he's a really good boy as well. If you look at his career so far, albeit in U23's and England youth teams, he's achieved some amazing things really.
"It was the right time for him to come out on loan, we felt we were the right club and so did he, so I'm really pleased he'll be here until the end of the season."