The commercial PHP development IDE PhpStorm can be used to develop Piwigo plugins and themes. It has a lot of functionality and if you buy it for personal use it is not that expensive. As a student you can get a free license.
Before starting modifying or developing your own Piwigo themes it is strongly recommended to read the theme development documentation available on the Piwigo website and the Smarty manual. The documentation is not extensive, but enough to get you started with already existing themes as a base.