Maximizing usage on one drive only while the others are idle is unlikely to be optimal, watch the drive light, they are not there just for decoration. For a properly set up system the lights should look like Christmas in a disco. Linux offers software RAID but also support for some hardware base SCSI RAID controllers. Check what is available. As your system and experiences evolve you are likely to repartition and you might look on this document again.
Additions are always welcome.
Work is also expensive, make sure you get large enough disks as refitting new or repartitioning old disks takes time. Think reliability, replace old disks before they fail. Keep a paper copy of your setup, having it all on disk when the machine is down will not help you much. Start out with a simple design with a minimum of fancy technology and rather fit it in later. In general adding is easier than replacing, be it disks, technology or other features.