The Toffees are the only Premier League team not to make a permanent signing over the summer, although they have acquired Eric Dier on loan from Sporting Lisbon.
"I'm not in the business of coming into football management to sell my best players. I won't do that," he said.
"But if I get an offer which is right I will, and I'll never let Everton get into trouble."
Everton begin their Premier League campaign tomorrow at home to QPR after their opening day fixture away at Tottenham Hotspur was postponed due to rioting in London.