Capacitive Touch Keyboard from Uno to a standalone 9V powered ATmega328

Hello!

I’m hoping to make the circuit above work from a 9V battery and an ATmega328. I have it working on my Uno with USB power from my laptop, but I’m hoping to make it work from a 9V battery. I know the Uno is just an easy development tool for an ATmega328, but I’m uncertain what parts of the Uno circuit must be retained for this to work from a 9V battery.

I know I’m going to need a voltage regulator to force the current down to 5V, but beyond that I’m a little uncertain because this is my first time trying an Arduino project… for instance do the crystal/ capacitors that often come with ATmega328s need to be used?

Apologies for how basic this might sound!

(Note: I’m not asking how to program the separate ATmega328 or anything, I understand how to set that up.)