Autoscaling set-up on EC2

I'm new to web development and design (I moved over from construction where answers are much larger), and I'm trying to build a scalable AWS architecture for a Wordpress site that lives in the free tier but will ramp up to meet demand. Is there a single EC2 instance solution to have my web servers autoscale and clone so that changes propagate throughout the tier, without having to manually update each instance?

My search has put me on nginx and heartbeat or corosync as possible software solutions, but I really don't know where to look to implement this on the cheap.

EDIT: now looking to rsync and incron, but will having all server instances push changes out cause an infinite loop on change?

Give yourself a "Gold" instance whose sole purpose is to update your website. When you do a site update, run the instance, update your site, stop the instance, then make a fresh AMI image of the instance.

Once you do that, update your autoscaling group to launch copies of that new AMI image. Terminate instances that are using the old AMI image.

This way, you only update a single instance.