Why don't you order the starter pack and get 4 different beans selected by Andy?
Failing that if you really want smooth...here's my 2 bob's worth.
4 bags: either of the brazils; peru ; colombian or mexican; sulawesi blue
or a bit more variety
either of the brazils; peru or colomb or mexican; sulawesi blue; any of the Ethiopians (Yirg / Gambella / Sidamo / Harrar) or Tanazanian
You can make a smoother version of a Mocha Java from the second list by using a 50% brazil base / 25% each of Ethiopian and Sulawesi.
You'll work out what you like as you go along