I'm opposed to the expensive microphone idea. You can make do with a cheap lav mic but its gonna cost you time in processing after recording. But if you want to reduce time in processing, an expensive mic will do you well.
If you really wanna go all out on expensive mics get an AT2020 and a Focusrite interface. Focusrite being the cheapest, trusted, and durable interfaces in the market. AT2020 being one that sounds good, cheap, and durable in its own market.
If you're just doing it maybe earn a couple of extra bucks, a samson c01u should suit you well.
If you're just doing it for the heck of it, those 20 dollar usb mics from ebay is enough.