Newcastle still don't have a world team, but they are good enough to finish in the second tier of England. They won't be 3rd this season, but I don't think that's the goal either. They just want to finish with the best 6-7 and then hope that they can bring in some reinforcements again next season.
Newcastle has made an impressive start to the season, currently sitting third in the Premier League table with 30 points, seven points behind title leaders Arsenal. So far, they have only lost one match, against Liverpool in August, and have won eight and drawn six games. They have the potential to remain in the top four of the Premier League this season.
They have so much money, they can pay every player in the world and they can pay all the salaries as well. Mbappe wouldn't be a problem either, but the problem with very good players and stars is that they have little interest in playing for Newcastle United. Of course, PSG and City also started this way.
If they can make it to the Champions League, I see no reason why world-class players will not sign for them, because their new owners are ready to compete in the Premier League, and they have been trying to bring in world-class players.