At your skill level, for an on-camera flash, keep your life simple and get the TTL version. There is still a bit of learning involved to get the very best results consistently, but it'll get you in the right ballpark 99% of the time.
That said, start playing with / using it in manual when you can to learn how to best control your lighting without TTL. Even after you learn how to rock it in manual, there will be times when TTL is more appropriate for the situation, so it'll be good to have it when you need it.
And, THAT said, start thinking about taking the next step by getting it OFF the camera and firing it remotely with radio triggers. Then you can move on to light modifiers like umbrellas, soft-boxes, umbrella-boxes, reflectors, multiple lights, and more. THAT is where you'll see HUGE improvements to the kinds of photos you can make.
Get lots of info towards those later steps here:
Strobist and click on "Lighting 101".
Edited to add: The myth that you need to spend big bucks on expensive Pocket Wizards to get TTL radio triggers is just that: A myth. You can find 3rd party TTL triggers much cheaper that work just fine, if you decide you want to go that route.
Also worth noting, when your flash is off camera, that usually means it's on a stand or a clamp pointed at a subject, and neither are going anywhere for that particular set of photos, and THAT means that you don't need TTL, because when you're setting it up on the stand and positioning your subject (a person OR thing), you can set the flash power appropriately then, especially after you've had a little practice with how much power to push given distances.
Of course, if you and your subject are moving around a lot and you've got an assistant(s) willing to hold and aim your light(s) for you, then maybe TTL would work better for you. Or maybe you could just tell the assistant, "turn it down 1 stop" (for instance) since they'll be standing there holding it anyway.