Dear Mike,
My name is Giulio,I leave near florence,in a little old hill where i have open since 1996 a bed&breakfast and where we organize cooking class, wine tour and spice aromatic tour.
In answer of your questions:
If you are making a pizza with only one spice dipending which pizza you are preparing!
If you are preparing a classic margherita the best is origano
If you are preparing a 4 stagioni the best is timo
For a tomato sauce the best spice is hot pepper
If you want to have more info you can visit me at www.lalimonaia.net