Humidity controlled fan

Not sure where or how to start this project but essentially there is a product called Cigar Oasis which is an active humidifier. Simply, it’s a fan that sits over a piece of floral foam filled with water and it turns on when humidity is lower than a certain threshold. I didn’t want to spend $120 for something that did such a basic function so I wanted to build my own, just not sure where to start.

What I want to do is build a device with a small oled screen and two buttons. I want the screen to display the “current humidity” and “temperature” and a “set humidity to”, which will be controlled by two buttons, one for going up and the other for down. When humidity gets below the set percentage for a period longer than two or three minutes, I want the fan to kick on and cycle until it reaches the set point and spin for another 45 seconds.

I know I want to use something like a arduino nano since I want it to be self contained and I’ve been told that I should use something like an HTU21D for a sensor instead of a DHT22. Again, open to any thoughts.