Moyes is yet to make his first signing as United boss after seeing a joint bid for Everton pair Marouane Fellaini and Leighton Baines rejected on Monday.
And the former Toffees manager, who also failed to lure Cesc Fabregas from Barcelona, says he will not be pressurised into signing players.
"There is a need to do it but there's no pressure to do it," said Moyes.
"It's something we've been talking about it since I took the job on July 1.
"I have an idea of where I'd like to strengthen but we won't do it because people tell us we should be signing players.
"If the right players are available great, but if not the first thing we'll do is encourage our own young players in the squad to do as well as they did last year."
Moyes confirmed United have the funds to compete in the transfer market, saying: "Yes I do (believe there is value in the market). But we've only targeted certain players.
"We don't have a big, big list because there are only certain quality players we want to bring in to the club."
And, ahead of Monday's home game against Chelsea, Moyes again insisted that Wayne Rooney will not be moving to Stamford Bridge after two bids for the striker were rejected.
"We have told you haven't we," said Moyes. "I hardly need to repeat it again. It doesn't need to be said."
Meanwhile, Moyes confirmed full-back Rafael would be missing for "three or four weeks" with a hamstring strain.
In addition, Nani (groin), Ashley Young (ankle) and Javier Hernandez (hamstring) will miss out against Chelsea as they recover from their respective injuries.
"Really they are coming back from the effects of not having a proper pre-season because they came back from international duty a bit late," said Moyes.
"Hopefully they are all not too far away now."