Villa picked up their first win in five matches with a 2-0 win over Cardiff City on Saturday courtesy of strikes from summer signings Leandro Bacuna and Libor Kozak.
The pair cost in the region of £10m and Lambert indicated Villa will continue to target players of a similar profile in the January transfer window.
"That's the game...it's a challenge," Lambert said. "Randy has been great and (chief executive) Paul Faulkner has been great but we won't be able to do what you would call a massive signing.
"We won't be able to go out and buy the big type of players. We have to look at the market, the young lads. We give them an opportunity and hopefully they take it."
Lambert is working with a thread-bare squad at the moment and has regular first-team players Andreas Weimann, Gabriel Agbonlahor, Fabian Delph and Antonio Luna unavailable due to injury.
The 44-year-old Glaswegian is relieved that the international break means Villa's next match is not until November 25 when they travel to The Hawthorns to face city rivals West Brom.
"If you look at the side we put out against Cardiff you'll see we have lots of injuries at the moment, nearly half a team out," Lambert said.
"You know things are bare when you're putting young kids on the bench as we did.
"We had to make sure we got through this one and thankfully we seem to have done that with the win.
"If we get three or four of them back for the West Brom game then good. All things being okay, we'll get a few back."