Im with @Trik with this one, if you cant afford the audio interface just yet, then dont. you dont have to force yourself into buying one. like @Fade said, Master your DAW, from there youll figure out a way to maximize your setup even if its just a laptop and headphones. Besides, its not what you use, its how you use it.
I can give you an advice that can probably help you afford that setup including the audio interface....
"Torrents"
you can probably figure it out from there.
i cant believe how wrong everyone on this thread is...
you HAVE to have a complete analogue studio - its ALL about what gear you have - fuck everything else