conky run

In your conky config, add:

own_window yes
own_window_class Conky
own_window_type override

This line keeps conky from getting controlled by the wm:

own_window_type override

You'll also want

background yes 

(its set as 'no' near the top of your conkyrc) to launch in the background, once your config is all set. Or launch with the daemon flag, -d.

Source: https://faq.i3wm.org/question/3829/conky-on-desktop.1.html

You mentioned compositing, while not needed for this, if you end up looking for something for compositing features (ie transparency) check out compton. Not sure if something newer and better has popped up but its decent and lightweight.

Also, welcome to the i3 community!