It is hard to decide where to start. I have been reading (and occasionaly writing for) Coin World for something over forty years. The main focus of CW is United States coins. Therefore it is less essential if you are interested in exclusively or primarily in world material or medals/tokens. Still you will find information on this type of material too.
Have found Coin World full of numismatic information and read it every week. It is one of the best numismatic newspapers avaialble
This publication covers it all then some. World currency to US cents and then some; this one is the one to subscribe to first!
Coin World or Numismatic News? I've been getting both for the past year and Coin World is clearly better. The news coverage is deeper, the letters to the editor are more insightful and it has more advertising. If you can afford both, get both, but if you have to choose, buy Coin World.