Suspenders is a gem by Thoughtbot, a well-known Rails consultancy. It's likely a good choice for you if you buy into the Thoughtbot ecosystem of gems and like working with services like Heroku and CircleCI. Free to use under the MIT license.
Rails Apps Composer
Rails Apps Composer is an open-source gem maintained as part of the RailsApps project. It helps you create a starter app from the command line or save your own boilerplate as a re-usable application template. It will even walk you through various options and allow you to create your own perfect "recipe". Free to use under the MIT license.
RailsKits is a SaaS product from a company called Koombea. It focuses on payments, providing models and controllers related to setting up accounts, users, and subscriptions. It supports a wide variety of payment gateways, from newer services like Stripe to older ones like Authorize.net. Pricing starts at $249 per project and goes up to $999 for a guided setup process.
Bullet Train is a SaaS service that helps you generate advanced scaffolding for your application. It sets up a framework for subscriptions, user management, teams, and security settings. It also provides a command line tool to generates models, controllers, and views with a deeper knowledge of your application than the standard Rails scaffolding offers. Pricing starts at $950 per project per year, with a substantial discount for additional projects or additional years of usage with the same project.
Rails Application Templates
Rails provides a mechanism called Rails Application Templates for setting up your own re-usable template. You can set up your preferred defaults as a script and use them in your next project. The primary focus seems to be on the gemfile and initializers, but there are options for generators and running one off commands, so it could be quite powerful. Free to use under the MIT license.