LarryD:
I would recommend you buy an Arduino UNO
Hi lindhoutd,
You will find lots of helpful members on this forum, but they don't always agree on the best approach!
I would stick with your mini, you don't need an Uno. The two boards share the same chip and are almost identical. For me, the advantage of the mini is that you can plug it directly into your breadboard for prototyping.
What you will need with the mini, that comes built in on the Uno, is a usb to ttl serial adaptor. This connects to those pins sticking out sideways from the mini and allows you to program the mini from your pc. Once your program is working, you can remove the adaptor and use it on the next project.
Where I do agree with Larry is that you need to start with simple tutorials first and get familiarised with everything a bit at a time. Throwing everything together at the start and expecting it all to just work is bound to fail.
Tell us more about the capabilities of the lcd you want, and what you mean by air quality. Perhaps we can suggest suitable components.
Paul