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. 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 Newcastle manage to finish the league among the top 4 teams this year, they may be able to attract the attention of high-profile players next year. For example, if they had played in the Champions League this year, they might have caught the attention of Cristiano Ronaldo. I think Mbappe will not be a difficult transfer for them. Mbappe's interest in money is also a known fact. If Newcastle make a good offer for him and they manage to qualify for the Champions League this year, they can sign Mbappe in my opinion. Also, it might be easier for Mbappe to change his mind if they sign up for a few more star players before they make a transfer offer to Mbappe.
I can say that the initial plan of Newcastle United is to end the league above 10 in the table or in the best scenario to be able to go to the Europa League but as the fact and matter is going it seems that Newcastle United is more lucky to have entered the top four in the first phase of the English Premier League. this time around they will have to do everything within their power to remain at the top four and when they are able to go to Champions League next season they will be able to sign any player in the world. What players want is money and to be able to play in Europe competitions.