The Customizr WordPress theme that I use at this site is an advanced theme that has plenty of options to change it to your liking. If you want to customize it even further, you can create a child theme and do that. If you are using the Customizr theme then there is an article that explains how to do that.
You can use a plugin to create a child theme in one click. It is called Childify Me. It is the easiest way to do it and the fastest. You just need to install the plugin, activate it. You need to supply a name for the theme. You could use Customizr Child or Child Customizr or something similar.
If you go to the Dashboard and click Appearance -> Editor you will be able to edit the styles.css and the functions.php files of your new Child Theme.