You know Alex Day right? Singer? Song writer? general purveyor of awesome via YouTube? well he's someone who can never EVER be copied but here are some tips to get pretty close.
Try the minimalist approach. While you don't have to go the whole way and strip down to only six items, it is easier to achieve this if you don't own thousands and thousands of clothes
If it's really weird, buy it. The whole point of his style is being completely whatever you want and not caring what everyone else thinks, so if you see a really odd hat that would not be accepted by your peers but you thinks is awesome anyway. Go for it.
Throw things away. Be able to get rid of the clothes that you don't want because Alex's' style is all about change.
Make sure this is what you want. Maybe tryout the look before you throw everything away because some people really can't pull it off and you don't want to be left with nothing.
When trying on the look ask someone who's opinion you can trust whether you can pull it off or not
Don't fuss about it too much, it defeats the purpose
If you're struggling to find anything try eBay, you'll be surprised what you can find