Downloading themes or plug-ins from some random place on the internet and not the official and reliable sources, or developers, will maybe save you some money but what ends up happening is you can end up installing all sorts of spyware on your web domain, not to mention the code quality that can be poor and potentially harmful for performance. Watch out for crappy themes and plugins and take the time to analyze the market that you are entering to get what you need for your WordPress.
If you are looking for a versatile CMS solution, you might want to check out Joomla. Joomla is a CMS that is rich with features and suitable for building and managing both small and large web applications. Joomla allows PHP ( yes, this is yet another PHP based CMS ) developers to create custom web applications and extend existing platform features. It is open source, and anyone can extend the functionality of the core Joomla system. Joomla is using a powerful templating system to build web pages, which makes it easy to create professional looking websites very quickly.
Git is an open-source, distributed version control software system that was created by Linus Torvalds in 2005. in order to track changes to developer’s source code, or other digital files, and enables users to revert to previous versions if needed. The Git database is stored on each user’s computer, allowing developers to work on projects even when they’re not online and are working on local development environments.
Drupal is an open source, PHP based CMS solution, very much alike but also different than WordPress.
If you want to host your own web app, first question to come in mind is what CMS platform I might, or should use for this purpose.
Learn how to recognize and avoid mistakes in WordPress theme development.