On your question of whether or not to repot Ruby after she's done blooming, it depends on the last time she was repotted. If you recently bought her and are unsure I would definately repot when she's finished up. You never know what may be lurking underneath!
Even if the bark looks good on top it may be like dirt in the middle. I just finished repotting one of my paphs I got at an orchid show last month and was shocked at the poor condition of the roots. I think that if I had waited any longer she'd be a goner.
As for the type of potting mix to use, they do make some especially for paph's. But I think people usually use a fine bark mix with maybe some sphag, perlite, charcoal, etc mixed in. I use medium coconut husk chips mixed with perlite and charcoal. That mix works well for as I tend to underwater so it helps things stay moist for a day or two longer. I think paphs like things a little more moist than phals but be careful if it's in fact in an older mix. Older media tends to retain moisure longer so make sure before you water. I'm definately not an expert but those tips have worked for me (so far!). Hope that helped!
Paph's Maude's Ruby blooming
everyone just thought I would show off 
I am a bit dissapointed that the color is not as intense as the photo's I have seen. But I love her anyway 
Maude's Ruby
oh well that leaves one space open 
Repotting Paph
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