Celtic manager Brendan Rodgers does not want to "stockpile players" as the January transfer window nears its end.
Rodgers has this month recruited forwards Vakoun Issouf Bayo, Oliver Burke and Timothy Weah, the latter two on loan, and has been linked with several right-backs.
The Premiership leaders host St Mirren on Wednesday.
"They have to really be able to make a genuine difference," said Rodgers of potential captures.
"If you're not spending maybe a lot of money on that then you always have to be careful that you just don't stockpile players. I'm always conscious of that. You'll always wait for quality.
"We know we have areas that we want to improve on in the team but we can only do that with players that will actually make us better."
Rodgers confirmed Chicago FC United right-back Andrew Gutman has been "working with the reserve team", with the American featuring in a Celtic XI that lost to Arbroath in a friendly on Saturday.
And the Celtic boss was asked about a possible move for Porto right-back Fernando Fonseca, replying: "I've got nothing to say on any players."
The manager says "there's been interest" in defender Jack Hendry and winger Lewis Morgan, who could go out on loan before the transfer window closes in 10 days' time.
Forward Odsonne Edouard has returned to training but is unlikely to feature against St Mirren while his fellow Frenchman Olivier Ntcham is expected back in training next week.
Right-back Tony Ralston picked up an ankle injury in Saturday's 3-0 Scottish Cup win over Airdrieonians and is to have a scan while Rodgers says there's no timescale on left-back Kieran Tierney's hip problem and is unsure whether the Scotland international will require surgery.
"We miss a player of that quality, there's no doubt," said Rodgers of Tierney. "He's a player that can really make the difference and does make the difference for us. But he's also a young player that you can't rush.
"He's a really tough boy, Kieran, as well as an outstanding player so you know that when he can't play because of the pain then you know that's for real."