Have you use any app to create static banner? I don't know how to code so still find it confusing.
They're just images added to the sidebar and other places hyperlinked to a page regarding an offer or in the case of my newsletter it has a signup box under it. My Newsletter/Subscription banner/image and signup box appear on every page of my site as I have one in the sidebar and one in the footer. More than enough and no need for an annoying, resource using popup.
I have also created a 10% discount coupon for every subscription and that offer is displayed in the banner/image. I used to use the Mail Poet newsletter plugin ... and the coupon code was displayed on the Confirmation page after they signed up.
Here is an example newsletter signup banner for an old site I made a couple of years ago called "Reality Stuffed" (realistic stuffed animals) I no longer use ...
It's a bit amateurish ... but I've improved since ... lol
I now use Mailchimp to do the same thing (Newsletters) ... as well as other things like Abandoned,Carts, Email followups and all the Transactional emails.
do you set any conditions for your banner to show on your site? (date, time, target customer, pages, etc.)
No. They are permanently displayed. Nice an simple. Using something to set conditions would defeat the purpose of keeping it simple and reducing page load times.