Johnson's team's second-tier status was ensured when they drew 2-2 at Blackburn and Milton Keynes Dons were relegated.
Chief operating officer Mark Ashton has said the club will "leave no stone unturned" as they look for new players.
"You couldn't name a player in Europe that we don't know their situation," Johnson told BBC Radio Bristol.
"We have a big summer ahead. That's the fun bit - the team-building process. It's exciting.
"We have got a bit of room to wriggle because our loans go back.
"We've got a good recruitment system - a decent scouting network of experienced scouts.
"I've got my ideas in the way we want to play and we'll recruit around that."
Bristol City boss Lee Johnson says he is excited about this summer's transfer window now his side have guaranteed their survival in the Championship.