Replying to Storage Help

Yooo, recently I've gotten way more busy with my filming and photo work (personal and client wise) and have found myself running out of space fast. Currently I'm running an iMac setup and just two lacie hard drives (1 1TB, 1 2TB) and am looking for a storage solution and have found endless options, but never any preference or recommendation over one another by others. Basically I'm looking for something I can backup onto and possibly edit off of so I don't have to fill my computers internal hard drive up. My budgets also fairly small for storage (under $500) What do you recommend? What's the best system that's worked for you?