The optimal environment is if you have plenty of disks to put the system, tempdb, logs, data and indexes on different physical disk arrays. you could even partition your data on separate disks depending on your database design. the overal best performance for the data and the index disk is RAID10 and for log and tempdb RAID1 because the latter are used mostly sequentially.

But all those advices are valid if your database is quite huge (over 50-100 GB).

below that size you wouldn't experience any performance gain.

A proper database design and indices as well as fine SQL queries are much more importants