Final Year Project

Hello I’m a third year student doing IT Support and for my last year I have to complete a project, I have an idea of doing an on-line shop but I’m confused as to where I start, do I build the website first or set up the database on a server? Also I know there is java scripting involved I’m just confused as to how it all comes together? Also any Ideas of a different project I could undertake would be greatly appreciated??