Web hosting companies will love to convince you that the more traffic you site gets, the faster (and thus more expensive) a server you will need. While this is technically true, in today's world it's a woefully outdated piece of advice that doesn't account for some recent technological advancements in hosting, namely caching.
When you host a site that is delivered to a user directly from your server, that is a very "expensive" operation. When a user enters your URL into their browser search bar and hits enter, your server will then have to go back, query the data, compile it into a page and then serve it to the user. This happens very quickly (think milliseconds) and though each individual operation isn't very taxing, when the server has to do that for every single visitor, it starts to become very expensive.
Here is where caching steps in, caching is typically done through a CDN provider like Cloudflare of Litespeed Cache. Going back the the previous example, if a user goes to your site, the CDN will reach back to your website, get the page the user is requesting a serve it to the user. The magic happens when another visitor requests the same page. This time the CDN will not go back and query your site; rather, it will just serve the same data it served to the last user.
As a result, your server costs will go down, your visitors will experience a faster site, your site will be more SEO friendly (since it loads faster), and to top all of this off it will cost you either nothing or next to nothing.
I won't be diving into the specific of how to setup a CDN in this article as there are plenty of guides to do so but the best place to start in my opinion is Cloudflare. Once you create an account, you can follow their step-by-step guide on setting it up with your website.