It really depends on how much you spend and what you want to do. I started using my laptop mic. Eventually I bought this handy little mic from Samson : http://www.amazon.com/gp/aw/d/B001R76D42/ref=mp_s_a_1_1?qid=1435414083&sr=8-1&pi=AC_SX200_QL40&keywords=samson+go+mic&dpPl=1&dpID=41PnZwr0rWL&ref=plSrch
I recently upgraded to a Yeti Snowball. I got a swivel mic stand that I mounted to my desk and a pop filter. I like the sound better, but I have to sit very close to it because the gain of the mic is a little lower. I also take it over to John Gholson's house when we record Slam Masters in the same room together, and I find it to be very versatile.