The best practices badge criteria are focused on increasing the likelihood of developing good software. Neither it nor anything else can guarantee success.

In particular, you can develop high-quality software that does not solve a problem that anyone else wants to solve, in which case it will not be a success.

Guarantees are hard to find. That said, I think it is wise to look at the practices of successful projects and try to copy them where they make sense. That's what this set of criteria does. If you want something that absolutely guarantees success of your project no matter what, then I'm sorry, I don't know where you can get that.

You're right that doing this requires time. In particular, if you don't have a test suite, picking a test framework and using it to create a test Suite takes time. I think it is time well spent.