I'm no pro at welding, but my welds are getting pretty decent. Learning to weld on thicker metal is easier, but welding on tubing will teach you heat control and how to fix blow-through. Here's what I can see:
The pic doesn't show any blow-through, and not much penetration, so I think you moved around too much. You need a steady hand making deliberate movements. That weld looks like you were moving wildly, and probably had the wire speed up too high.
Get your fit-up tighter. That gap on the right side tells me part of your problem is that you're trying to weld air. If the metal fits closer together it's easier to weld. Gaps like that require you to do a lot of "stitching" and sometimes you even need to build up the metal on either side of that gap just so you can weld it closed.