Someone shared a boilerplate template on the Elixir subreddit the other day, might help out. Can't really recommend anything for Stripe, though. From what I've seen people usually use Stripity Stripe.
I'm the author of the boilerplate mentioned here if people have any question about it, thanks for sharing! I've had the same struggles personally when building my web app so that's why I backported some my code into this repo, the defaults with Phoenix are great but there's a long way to make it kind of usable for real users.