Hello
Little bit confused about project description.
What kind of template you want? Like WordPress theme? Fully developed theme that you want to use on your 500 website?
Or AdSense ads code template? Its mean its also possible to customize AdSense ads code to make it fit on any site.
Whatever you thinking, I can make other way solution as AdSense expert.
If WordPress based template, I can setup on WordPress theme as your choice and will do fully customization. You can just clone it on all of your site to make it working. As it will be already optimized, you don't have to touch the AdSense ads code.
Also other ads like taboola, dfp etc.
For own banner, dfp best. Also you can use direct image/text ads. i will do the changes so you can easily change it.
Know me what you really want so I can plan as your need.
Price can be changed based on your plan.
Thanks
Moin