The hardest part of WP plugin/theme development is learning how hooks and filters work. Once you've got those down, you get can get wild.

Some great starter plugin resources (in order of my personal preferences for style and organization):

  * https://github.com/DevinVinson/WordPress-Plugin-Boilerplate

  * https://github.com/hlashbrooke/WordPress-Plugin-Template

  * https://github.com/mattyza/starter-plugin