I don't know of any one on our forum who grows their phals in potting soil of any king. most use either sphaphnum moss, bark or a mix. I use a mix of small bark, perlite (that white stuff) a little crushed charcol. This mix requires more frequent watering than using straight sphag, but it does avoid overwatering. You can also use a bark mix and add some chopped sphag to it to up the moisture retention.
While your plant looks good now, you should watch it carefully to make sure that it doesn't stay too wet with that soil in the pot. Again, most of us repot our plants when we buy them just to make sure they are okay and that they will fit in with our watering schedule.
good luck with your first orchid!