New to Pi, help me know what parts I need


I’m building a greenhouse raspberry pi device.
I know how to program in python and how to handle raspberry pi through CLI.

What I don’t know is what parts I should order for my project, here’s the requirement :
-Monitor the humidity level of 5 different plant pots (5X Moisture Sensor for micro:bit )
-Have ambient air monitoring (1X enviro+ board)
-Have 4 different programmable electrical relays for 120V A/C electricity (No clue where to start here)

Can all of this gear be plugged in at once from a single Raspberry pi ?
Please suggest me what parts I should order for this project, it doesn’t have to be a fully complete list of components but at least a direction where to start will help !