Making a New ebay Fire Phone (ATT) initial set-up guide- please help with "step 3"

My Fire Phone will be arriving from Ebay tomorrow (new, ATT unlocked version) and wanting to figure out the best steps to optimize it before it auto-updates to 4.6.4. Lots of great info in these threads, but I'm a bit uncertain about the correct steps to take once my phone arrives. Figured a bunch of people are in the same boat, so I'm trying to write a quick guide and hope to draw from people's experience here.

Step 1:
Activate Phone with Amazon to get free year of Prime. Follow guide at: spinyourfire.com/fire-phone-tips-and-tricks/register-fire-phone/

Step 2:
Unlock phone using code from Ebay seller.

***Step 3:
This is where I'm a bit confused. I know that gApps work best with 4.6.3, but that ATT versions automatically update to 4.6.4, which is not gApps friendly. It sounds like downgrading from 4.6.4 is time consuming...
So what do people rec is the best initial step? Should I turn off automatic updates or is there a better course of action? Maybe I need to install root/Safestrap and then use the stock 4.6.3 image?

Step 4:
Install gApps following the guide at spinyourfire.com/fire-phone-tips-and-tricks/turn-fire-phone-into-android-phone

Step 5:
Conserve battery life:
Disable Tilt/Swivel/Dynamic Perspective/Peek/Auto-scroll – Go to Settings > Display > Configure low motion settings – Enable ‘Low Motion Mode’
Disable Bluetooth, NFC and any other features you are not using.

Step 6:
consider more advanced options such as Root/Safestrap in order to make CM11 or SlimKat possible (see developer threads.) Also consider adding an alternative start screen and/or Google Now.