Technical side: choice of instruments and effects that you choose to implement your arrangement.
Now, failure in any of the three can ruin the track and not uncommon even among experienced folks. Failure in any of the two makes a track unlistenable and failing all three will make a track a disaster. The problem for beginners is that they are not good at any of the three so normally what comes from the beginners in tracking falls into the disaster category. But that is how you learn.
However it is possible to make learning process easier if the tracker addresses one area at a time. What you could is choose an existing melody from a track that you like the most and try to rewrite it following its original arrangement. In this way you will learn the technical side. Trying to make the track reasonably close to the original is the key but of course it does not have to be an exact copy.
Once you’ve done it, take the same melody and try to make your own arrangement. And once you can arrange yourself well, then all you have to do is to come up with a killer melody to get to number one in charts!