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
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 Raspberry 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) 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?