Wenger broke the club's transfer record to land Mesut Ozil from Real Madrid for £42.5m on deadline day, and Pires wants the Frenchman to continue to use the Gunners' cash.
"If you look at all the successful clubs who won titles and trophies, they always buy after they have been successful," Pires told The Mirror.
"There is no question that Arsenal are at a high level at this moment. They are playing to the kind of football played during my time at the club. And Ozil – well, he is world class.
"But there appears to be a new financial philosophy at Arsenal now. Arsene can spend money, more than he has been able to do before and I believe he should add to the squad when he can."
The Gunners are currently top of the Premier League.