Free plugins
These plugins are a "must" for styling Confluence, and they are all free
Customware Visibility: http://wiki.customware.net/repository/display/AtlassianPlugins/Visibility+Plugin
CustomWare Redirection: https://marketplace.atlassian.com/plugins/net.customware.confluence.plugin.redirection/version/12
Confluence Advanced Macros: https://marketplace.atlassian.com/plugins/confluence.macros.advanced/version/30120
Adaptavist Content Formatting Macros: https://plugins.atlassian.com/plugins/com.adaptavist.confluence.contentFormattingMacros/version/205
Web / CSS for Browsers
Chrome
Firefox
3rd Party styling tools
Personally, take care when using these - all though You can achive amazing things beyond my capabilities, You are faced with tight integration affecting upgrades and additional licencing and costs.
https://marketplace.atlassian.com/plugins/com.adaptavist.confluence.themes.sitebuilder
https://marketplace.atlassian.com/plugins/com.refinedwiki.confluence.plugins.theme.original