Content is called a king and design must be the queen. Branding is important as hell. Choosing a unique and memorable logo and good design for your blog is crucial in making a successful blog. Simply browse through Themes on WordPress themes directory and choose the one that is clean, simple and portrays your blog's content.

If you have spare $30-$50 I would highly recommend you to go with Premium theme as you will get more unique theme, easier customization and premium support.

Some tips for quickly designing your logo or blog. Simply go with Helvetica font and your blog name. Make sure to choose right colors for your blog. Use COLOURlovers or Adobe Kuler to find a nice color palette for your brand. Quickly skim through the meanings of colors to check if your brand will be perceived correctly.