"They've made it clear to me we've got to try and get value for money, don't spend transfer fees," Warnock told Talksport.
"They've agreed to pay £1.25 million for Campbell but I can't see any other money changing hands, other than DJ Campbell, if I'm honest."
Warnock admits he felt the club would provide him with a bigger budget to strengthen his squad but is adamant his side can progress without major spending.
"I thought I'd have a few million, if I'm honest," said Warnock.
"I was disappointed but it's not the end of the world. It would have been nice to have money to spend but it's just another one of those things in my managerial career where I have to show what I can do.
"I look at the players I've brought in, Bothroyd and Dyer, and if I can get three or four more players of that quality, I'll be more than happy. I'm not despondent. I'd love money, every manager wants money. But it's not all doom and gloom."