WP Theming The most important resource for wordpress developers is supplied by the wordpress community themselves: the codex. If you're about to start writing your own theme, the articles on Theme Development and The Loop are a must-read. Also, even though you're just developing for personal use, it might be a good idea to familiarize yourself with the WordPress Coding Standards.
If you're not all that familiar with wordpress (yet), it would be relatively tedious to write your own theme completely from scratch, i.e. to start with an empty theme folder. For a starting framework, I'd highly recommend checking out the Starkers Theme by Elliot Jay Stocks. It is a framework built upon the TwentyTen WordPress theme, stripped off all semantic markup but containing the most essential files and functions a wordpress theme should have.
Modern Standards, HTML 5 & CSS 3 If you want to write your theme in a modern fashion, i.e. using an HTML 5 doctype as well as semantic HTML 5 structural elements, tools such as Modernizr and HTML 5 cross-browser polyfills can be included into a wordpress theme as they would be in any other ol' website.
Gallery As for the gallery, you might want to check out the NextGEN Gallery plugin by Alex Raabe. It is widely used, relatively future proof and can be styled to your personal needs.