I'd like to add footwell lighting when the dashlights are on. I had something similar in my Corolla, which was easy to tie into (ring around the cig lighter).

Any suggestions on the best circuit to hop into? Probably something in the waterfall block?

 

Do a search here for "footwell lights". One of the slots in the interior fuse block can be used, but I don't remember which one off hand.

 

I tapped into the back of either the hazard light button/traction control button on the waterfall. Just unplug the connector, turn on the lights, and use a multi-meter or test light to check. Been connected there for years with no issue.
My stuff dims with the dash lights.

 

You see the button that closes when the door shuts? Tap into that. It's great because it's right next to where you want the light