@Spin here is an article I wrote many moons ago describing the various raids with pictures and the underlying mathematics behind each one.
However, I would not recommend RAID 5 for large drives / arrays and will rather go with RAID 6 setup or even a higher setup if at all possible. The problem with RAID 5 is explained very clearly in this article here:
with the follow up article on why RAID 6 will need to be replaced in a couple of years time:
obviously, if you don't care about the data, then stick it in RAID 5, or you may even dabble with Unraid or whatever the flavor of the month is, but as soon as you start caring for your data, then stay away from RAID 5.
Regarding the server, take any R500 old desktop (preferably one with a Gb NIC, plug in a couple of hard drives, and call it your "file server". Will work as good as anything else for the purpose of a media-hosting server. When the HDD is full, buy another HDD and just continue plugging in more. If you are just starting out now and funds is a concern, then stop worrying about RAID, and redundancies, name brands, etc.