new orchid, help from making the same mistakes

[butterfly79]

I have a new purple phal. It is potted in a clear plastic pott with sphagnum. The roots I can see are green and firm, the sphagnum was very wet when I purchased it so I haven't watered it. The sphag is still moist and it's been about 6 days.
Now how often should the orchid be watered because all the info I have read is conflicting. Some say let the potting dry out and then water and others say keep the sphag moist for phals?
When the flowers fall off should I repot the orchid in orchid bark mix or should I leave it in the sphag. I have purchased 5 orchids in 2 yrs, none have worked out no matter how hard I work at it. I really want this one to work because these are my favourite flowers. I love caring for them. Any help would be greatly appreciated.