Customerise my existing blogger site with new template and theme

My site is here. This is free. I have a domain here but need a different template
https://www.blogger.com

General information for the website: Educational Website
Kind of development: Customization of existing website
Description of every page/module: I have a blogger site. I have my own domain name attached to it. I want a site that uses a better template. At the moment mine does not look professional. I know there are limitations with blogger, but I want the site to remain there as it is cost effective for me.
Description of requirements/features: I want a simple but chic design. I want to be able to use it without having to amend html. I will pay for the site once I have used it for two days, so that I know there are not problems or issues with html. I do not want a site that is so complicated that images and things start going over the page or not showing well. Something that works but is easy to maintain.
Extra notes: Someone with knowledge of customising Blogger site would be good.