Wolves have only made two new signings, with winger Fer Lopez joining from Celta Vigo and striker Jorgen Strand Larsen's loan deal from Celta becoming permanent.
Pereira told the Express & Star: "I know myself, at the end of the market maybe I will be not happy, maybe disappointed.
"I hope not, because I believe in the people that they are working hard to give us (players). We cannot do miracles, we need players.
"We need to compete with Manchester City, Arsenal. This is our league. We are not competing just with the clubs that are coming from the Championship. Even these clubs, they are spending a lot of money, they are investing a lot of money. It means that the next league will be very, very tough for us.
"I want players that I know that at the end of the game, we cannot control the result, but in the end of the game we are proud of ourselves because we fight, we give everything. Because this is the heart of the people in Wolverhampton."