Tim, you shouldn't apply "set up and forget" approach for facebook ads.
Test different audiences, creatives, wordings, messages, rich media options etc.
There are so many things that could impact your traffic and sales.
I advise you to learn a bit about ecommerce marketing, attend Virtual Ecommerce Marketing Summit: https://get.promorepublic.com/ecommerce-summit-2018/ It's free and you could learn from 5 experts from Shopify, WooCommerce, WordPress, NinjaOutreach and PromoRepublic.
Hope it helps.
Advertising is a constant game of tweaking, testing and improving.
If you don't freshen them up, the vast majority of campaigns become stale and lose their effectiveness over time.
There are loads of tools out there that you can use to split test campaigns. When you become familiar with the process of optimizing your ads, paid traffic can light a fire under your business and you can achieve huge growth rates. But you have to be comfortable with the testing and iteration process. Not every campaign will be a winner.
Before venturing into facebook advertising without knowing how to use their advertising platform is a bad idea. You will definitely learn new things while you are at it because facebooks ad platforms itself is pretty self explanatory and they give guide lines to help newbies.
But let me tell you one thing, It is in the interest of online advertising platforms like facebook, google, twitter etc... that people know how to use their platforms.
So that more people will use it and they will make more money. So all the advertising platforms have provided detailed instructions on how to use their advertsing platforms in a better way.
Facebook has "Blueprint" learning program where they will teach you all about running facebook ads and in the end you will even get a certification.
you can try the blueprint certification here : https://www.facebook.com/blueprint
I suggest you spend a day or two and complete theri certification course, this will let you know all the cool advertising options available in facebook that most people dont know to make use of.
Let me give you a glimpse of one such cool option. You can use a snippet of code called "Facebook pixel" for remarketing. Which means, you can track people who have clicked on your facebook ads.
There are lot many things you can do using facebook pixel as described in this article https://www.globalmediainsight.com/blog/complete-guide-remarketing-facebook-pixel-2/
This is one of many other features that most people starting out on FB ads wont use .
Let me know if you need to know anything specific about facebook advertising.