1st router bits to get

So check it out, i'm finally getting a router today once Sears open here.  I'm going with the Craftsman pro. 2 1/4 hp router w/ plung/fixed bases.  My question is, what are some necessary bits i should get first?  This is my firs time using a router, i don't know exactly what to do but ill be sure to figure it out pretty fast w/o messin anything up.  So yea, i'm basically only going to be using 1/2'' & 3/4'' mdf wood for my my projects, so which 2 or 3 router bits should i get first?  i'll mainly be doing speaker rings at first w/ it cuz i've got a pretty nice jig saw.  let me know what ya'll think

Richard