How hard is it to actually customise the template your given? I know design but not any html/css.
If you don’t know any html or css, don’t expect your site to look much different from whichever template you choose to install. I wouldn’t even bother trying to make any significant design changes yourself, unless you know html, css, xml, php, and the mvc model.
Also.. what am i supposed to download?
Each one is different.
To top one downloads in “installer” which then downloads and installs the latest version for you.
The middle one is the latest version of the files. There is no “installer”, so in this sense it is more of a manual process (but not completely manual, as there is an install-wizard that helps you set some of the configuration).
The bottom one is just sample data, so you can see what a store looks like with categories, products, etc.
I HIGHLY recommend reading all of the documentation on this site, starting with the user guide.
Magento is a complex (and well written!) piece of software and you really need to learn how to use it by reading the docs. Just going in and trying to figure it out as you go probably won’t work for most people.