Reply to Help a noob out :( pleaseeee

I dj purely for fun on my own. i am learning to beatmatch and all that jazz.

I would like to run Traktor with my Numark ndx900's and pioneer djm-250. The pioneer djm-250 does not have a sound card so i need to buy one in order to play songs off of my computer. right? please if i am wrong someone direct me because i don't want to waste my money, i really enjoy spinning on the flash drive but id prefer to have access to more songs.

what the fuck do i buy?