Hi Smith, and welcome to the forum!
There seems to be some disagreement about which grade OO is best for soap making according to the several books I've read on the subject. I'll say though that it appears most of the books say it doesn't make all that much difference, so cost might be the deciding factor. I've also heard that pomace has more non-saponifiables which might be good in the soap. I've heard that these impurities might accelerate or catalyze your batch and make it go pretty fast from trace to solidifying.
Please note that I'm a newbie so most of what I say is book learning. Perhaps the experienced soapers will have a better answer for you.
My own feeling is that it doesn't make a lot of difference, particularly between extra virgin, virgin and plain refined (one grade up from pomace). However, I have a good friend who is a professional soaper and she uses extra virgin.
I bought my OO at
Trader Joe's Market. I don't know why but the extra virgin and regular were both $6.99 so I got the extra virgin. You can see my results in my post "first batch" thread here in the forum. By the way the OO makes very nice soap. I added a bit of palm and coconut to improve the lather and hardness a bit. It's as good as any soap I've ever bought.
I suggest you go with either regular or virgin, and leave the pomace for when you get more experienced.
BTW my EVOO was $6.99 a liter ($26.46/gal or $3.45/lb, just for reference).
I'll be interested in hearing what others are paying for their OO.