Backing up is very important. One of my friends, 3 days ago, had his hard drive crash and he just lost all his photos of his baby twin girls for the last 2 years. He is looking into data recovery but the quotes he's getting is between $1500 - $3000. Not really an option for him at this time.
RAID is really not that complicated. It can be in certain situations but for the use you would likely be using it in, you probably wouldn't even be able to distinguish it from just another external drive other than the initial setup.
What I would recommend is to get something like this:
For you, probably a 2 disk enclosure would work well. I am currently using the Vantec one. There are many to choose from however. What you would do is buy three 3.5" hard drives, 2 to put into the enclosure. The third I'll explain later. You can buy any brand that you are comfortable with and any size. Just make sure that the three you buy are identical (don't have to be, but it would just make things easier for you). I personally like Seagate drives. I've had many WD, Samsung, IBM drives fail on me over the years. I've never had a Seagate fail on me yet... (fingers crossed, knocks on wood). However, other people I know have had terrible luck with Seagate yet had great experiences with WD or Samsung. So, whichever your lucky brand is, get those.
After inserting 2 drives into the RAID enclosure, set it up to run as RAID 1 (mirroring). After the RAID has built, you should be able to use it as a drive and it will look and behave as an external drive. If one drive fails, you still have an exact copy on the other drive.
Now, for the third drive, you can keep it bare and stored in a static free bag to use with a hard drive dock (http://www.amazon.com …&rh=i%3Aaps%2Ck%3Ahd+dock) or you can put it in its own hard drive enclosure. What you do with this drive is to copy all your files from your RAID drive onto this one and then take this drive and store it off-site. Keep it at work, a friend/family members house, safe deposit box, or wherever. Bring it back regularly to keep it updated. The reasons for off-site backup have been explained above I believe.
Another option instead of the 3rd drive, would be to use cloud backup. But, that depends on how you feel about storing your stuff in the cloud, your network speed, etc. Something like this might work in this case: http://www.backblaze.com/