Suggestions for RAID Hard Drive Set up

I am not a professional in any sense of the word. I am an amateur photographer and videographer. I am running a iMac, processor 3.5 GHz Intel Core i7 with 16 GB. I have tons of family photographs and videos. I am also a cyclist and take GoPro video of many of our long rides. My goal is to keep my Macintosh HD as empty as I can yet not lose speed. I have four external hard drives connected to my iMac using USB 2 connections. The hard drives are old. I am also experiencing frequent spinning beach balls, that I believe are caused by the slow USB connections. I am looking to purchase an RAID external hard drive enclosure that has a Thunderbolt connection. My expectation is to use the RAID hard drive not for back up, but rather for storage of my music, photos, and video files.

Looking for suggestions on configuration of RAID (RAID 0, RAID 1, RAID 10). I am looking at a minimum of 4TBs, probably 6TBs, cost being an issue. Also looking for suggestions for where to buy.

Hank