Dmitry Rybolovlev has funded the arrival of 12 players since their promotion to the top flight, including Radamel Falcao, James Rodriguez and Joao Moutinho.
However, their Italian manager believes it will take time for them to reach the level of last season's top three, and has called for patience ahead of the new campaign.
"Compete with PSG? I believe it is too early to ask such a question," Ranieri told L'Equipe.
"PSG, Lyon and Marseille look more like teams than Monaco. So we need time. It will be difficult to be champions this season.
"Give me some time. To me the most important thing is first to try to build the best group possible."
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