i am mainly from software background with very very basic level of electronics/microcontroller knowledge.

i recently did a small iot project for moisture/temp detection following this tutorial : https://docs.aws.amazon.com/iot/latest/developerguide/iot-moisture-raspi-setup.html at a very high level this uses raspberry pi4 and a capacitive moisture sensor (which is plugged into raspberry pi) to send the data via aws iot to my email.

I would like to upgrade to where i can have multiple stemma capacitive moisture sensors (1 for each of my indoor plants) without obviously buying many raspberyy pis...i did some basic research and i believe i would need some sort of microcontroller with each moisture sensor for each plant that is battery operated and can send data either on wifi/mqtt (something like this https://diyi0t.com/microcontroller-to-raspberry-pi-wifi-mqtt-communication/) or bluetooth...then my raspberry pi can act as a server to each of these devices send data to aws.

i kindly need guidance on what piece of cheap battery operated (ideally don't want to plug in)/wifi or bluetooth enabled hardware (microcontrollers?) is best for individually having many moisture sensors connected.

also is my thinking correct?