You don't have to download maps eh. At least I didn't. The one I got came with default set of maps, and if a server was running a map that I didn't have, the game would download it for me.
Read this
http://www.bosskey.net/cs/
Basically will describe the way the game works and has section called tips that should help you out.
other than that, it's just in time and lots of playing (if you do that) that you will get skill.