The Bolton manager made his first move this week when he secured Israel international midfielder, Idan Tal, on a pre-contract agreement.
"Some of the squad will come from free agents, some will be more heavily invested in," he said.
"We have to get some younger players in."
"Most of our players are signed towards the end of July or even into August," he said, "but we always have to do a lot of business in June to set up those deals.
"Unfortunately, June's going to be a waste of time because of the World Cup. So it's important that we secure a few players before then.
"It just means we'll have to work extremely hard in the summer to try to sign the sort of players we need to continue our progress, with less funds than other clubs.
"But I probably work harder in the summer than any other manager in the Premiership, even though they wouldn't agree, and this time there's going to have to be a lot of work done to get in the five or six players I need."
Meanwhile, Manchester United boss Sir Alex Ferguson is backing Bolton's Sam Allardyce for the England job.
"I think Sam has got an absolutely outstanding chance of getting the England job," said Fergie.
"He's got great experience and gets the best out of his players, as you can see with the job he's done at Bolton.
"You always know his teams are going to give you a hard game and it will be no different for us this time around, because Bolton are a very good side."