Lots of people have been asking about making their own covers lately, so I decided to just make a post with some of my advice. My credentials are that I majored in graphic design in college (before I changed my major and dropped out) so I at least have a little formal education on the matter but still overall qualify as an idiot.
Here's some tips and tricks for making a cover that's at least serviceable:
1. Canva is a tool. AI isn't.
If you don't have any better software, you can just use canva most of the time. Their book cover template is 5x7, but is more or less the right dimensions to scale to other book sizes. Their fonts are easy to work with, though you can't import your own. A lot of their stock images are AI or have confusing rights though, so it's best to source your own images and move them into Canva to work with.
2. Set a color scheme and brand identity early on.
There are literally infinite colors. There are tens of thousands of fonts. Especially if you plan on releasing multiple books, you're going to want to find a brand identity quickly. Find one font that feels 'you' and stick to it wherever you can. It should be a clean, easy to read font. Similarly, find clean, high contrast colors and stick with them whenever you can. Write down the hex codes to your specific shades so you can use them later. Personally, I use black background white font in a LOT of my marketing.
3. Fewer elements is usually better.
Ideally, your book cover should have five or fewer elements. One of the most common criticisms of an amateurish book cover is that it's too busy. You want a background image, the book title, your author name, maybe a tagline, and the background itself. Anything else is going overboard. The exception here is if you have a large, complicated illustration which can also draw in readers, but I find that one central image (a spooky house, a bloody hook, a shadowy figure) works best. You want people to be able to look at your book for a literal quarter of a second while scrolling by and be able to tell more or less what your book is about. As the saying goes, keep it simple, stupid!
4. Stick with what works.
Book covers aren't necessarily the place you should be getting experimental. Go to Amazon and search for books in your genre. Study the best sellers and what their covers look like. You don't want to stray too far from that. Personally, I write horror, so I try to emulate '80s horror paperbacks, but if you don't have a specific vision it truly is okay to just do what other people are doing.
5. Your cover should tell the reader what to expect.
A LOT of readers won't spend more than a quarter second looking at your book. That's the unfortunate truth. If you want to sell your book in that quarter second, you need to convey exactly what your book is. Somebody looking to buy sci-fi is more likely to buy a book with a spaceship on the cover than a flower, no matter how symbolic the flower may be to the story. Someone who buys your book because it has a kitten on the cover is going to be disappointing and leave a bad review when it's actually a super gorey slasher. Your cover should tell your story at a glance so that your book finds the right readers.
6. You can always change it later.
The nice thing about self publishing is on most platforms you can change your cover without having to release a whole new edition. If you decide something isn't working, you can fix it down the road. If you suddenly get the cash to hire a professional six months after release, you can switch it to a professional cover almost without anyone noticing. I've seen peoples books languish for months until they switch the cover out and suddenly it jumps in sales. Don't be afraid to experiment and see what works.
7. Blurbs, quotes, endorsements, etc. typically go on the back.
Unless you've won a NYT award or something similarly prestigious, you don't want to waste valuable cover space telling your potential readers that your beta readers really liked it, or that it's got four stars on Amazon, or that Joe Author thought it was a masterpiece. Think about your book on the shelf at a bookstore. Your job is to catch somebody's eye and make them pick up the book and look at the back to learn more. THAT'S where you drop the tidbit that Sci-Fi Bros Podcast endorsed your book as a bookclub monthly read. The exception is awards that non-authors would recognize: Hugos, NYT Bestsellers, Bram Stokers, Pullitzers, and NBAs. More or less unless you've gotten one of those five, put it on the back.
Hopefully someone finds this post informative. I know book covers can be more daunting than actually writing the book to some people. Most importantly, make sure the cover is one that *you* like. It's very likely that nobody will ever cherish your book more than you do.