https://www.revive-adserver.com/ - open source ad management software, create the zones you want, place the code on your site, and run as many pops as you want
Self-hosted version is completely free and is awesome, I use it on my websites!
No need to buy anything
You will get a code like this to use
Code:
<!-- Revive Adserver Asynchronous JS Tag - Generated with Revive Adserver v5.4.1 -->
<ins data-revive-zoneid="1" data-revive-id="42681811a07507d84390ab2dd8860024"></ins>
<script async src="/ads/www/delivery/asyncjs.php"></script>