AGK comes with examples, so don't overlook those because they will help you get started by showing you many basic principles.
Modifying working code is a great way to learn.
There are code snippets here in the forum too.
With the book, the examples, and the information here in these forums, you'll could be releasing your first app faster than you think.
Use the 'Search Forum' button to look for your answer before you ask, because it may already be answered saving you wait time for a response.
For sound effects, I use
SFXR.
For graphics, I use
Paint.NET (be sure not to click an ad if you try to download, because a lot of them look like download buttons)
Welcome, and good luck in your venture.

Coding things my way since 1981 -- Currently using AppGameKit V2 Tier 1