Filegroups and Storage

Hi,

I have upto 10 databases running on a single SQL Server instance on a single server.

I have read about best practice for storage and concluded the following...

1) Transaction Log on own RAID array (Raid 10) or at least on own physical disk
2) Data files(secondary filegroup) on own disk array (Raid 10 or 5)
3) Indexes on own filegroup (Raid 5)
4) Primary on Raid 1 or 5 (only system dbs)
5) Tempdb on Raid 5 or 10

So each of the above will be on separate physical disks?

Should I then have a separate disk for each secondary filegroup of each database? Or can they reside on the same disk?
How would this impact on performance?

And similar again with each Primary filegroup - should each one be on its own disk? In this case 10 separate disks for each primary filegroup?

Thanks!