Royals boss Brian McDermott is poised to bolster his squad when the next transfer window opens.
Arsenal winger Andrey Arshavin and Burnley striker Charlie Austin, a former Royals trainee, have been heavily linked with moves to the Madejski Stadium.
But Federici has warned that a spending spree could be a dangerous tactic, with Reading owner Anton Zingarevich set to back McDermott.
Federici, who returned to Royals' starting line-up in the 0-0 home draw with Norwich on Saturday, said: "We've been together as a good squad for a long time now. We have added a few players but I think there is a danger when you add too many players into a squad - you kind of break that team spirit.
"It's something we have here in abundance. You have to be careful who you bring in and the sort of characters that come in. It's alright for people who sit far away from the game and say, 'I want that player and that player'.
"But you need to look at their personalities and think, 'Are they going to fit into the group' before bringing in any players."
McDermott, though, is refusing to discuss potential targets and even suggests Royals may do little business in January.
"In the summer we brought a number of players for the future and the present and worked with the budget that we had," he argued.
"That would be disrespectful to the players we have here, these players are a great bunch of people. They are close, they are competing in each and every game there is no doubt about that.
"I never talk about players we haven't got. We will identify areas we think can be strengthened so I'm sure when January comes we can talk about every new player we want to talk about. The league we are in, you can't go and have a coffee without it being in the papers."
Federici, 27, was recalled by McDermott last weekend to replace injured keeper Alex McCarthy and duly helped Reading keep their first clean sheet of the season in the stalemate against the Canaries.
It was the Australian's first league start since the 4-2 defeat at Chelsea on August 22 and he will keep his place this Saturday when Everton visit Madejski Stadium (3pm ko).
Reading are still searching for their first win in the Premier League and they will need to raise their game to beat fourth-placed Toffees.
However, Federici argued: "I don't think we're that far away. I thought we deserved three points against Norwich and we deserved three points against QPR. That was my point with bringing in players. We've got it there, we just need to bring it out and show everyone.
"We still have the rest of this month, which is a big month for us. We got one monkey off our backs with the clean sheet. The next one will be the three points. It's just getting that one lucky break. Then getting 40 points out of 50 like last season would be lovely."
Federici was rarely tested by a toothless Norwich attack on Saturday, and stressed: "It has been a tough time for me but it is good to be back in the team and the boys worked really hard.
"Defensively we were very solid and deserved a clean sheet. Norwich are a good team but our boys were solid, which we have been lacking in the last few games, so it was nice for everyone to get a clean sheet.
"Now we look forward to the next game and Everton are a team very much in-form.
"But I think when you come to the Madejski Stadium it is a tough game."