the best choice of processor

I am using the arm m7, however I would like to use a cheaper processor to realize the following structure:
1- i2c output for OLED communication
2- two usart ports one for gps communication and one for gprs
3- a Gpio for communication with sensor.

I am in doubt between the m0 +, m23, m3. However if you have any other suggestions I would be grateful.
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