Here I am late to the conversation, but I love M & P soap making - you can do so much and so many different kinds with just a few ingredients (and without the danger and mess of cold process soap making).
I use either www.soapcrafters.com
m & p soap base. Soapcrafters is better but also more expensive. However you go, shipping heavy soap is expensive!
I get my fragrance oils from www.sweetcakes.com
or Soapcrafters - usually Sweetcakes. They are fantastic and I have about 30 scents, and have only disliked one. I add as much as I can smell in the soap. Scent "burns off" if you add it to super hot soap - let it cool down after melting, yet while it's still liquid. I find essential oil takes alot more to scent soap, is much more expensive and doesn't scent soap as long - so I usually use FO's instead. There's also much more variety in FO's than EO's, though EO's also have medicinal properties.
I also put in various additives, such as a half dropperful of olive oil or sweet almond oil per bar to "superfat"each bar of soap. I also use herbals such as lavender buds (for an exfoliating bar, it's scratchy), calendula petals (they stay yellow, very nice), green tea (out of a teabag), ground loofa (purchased), and colorants (usually I've just been using the stuff from Joanne's Crafts, or liquid colorants from soapcrafters).
You can get a wide variety of great looking/smelling/washing soaps by mixing soaps, colorants, additives, oils and FO's!
Have fun.... it's addicting.