First of all you need to consider what type of jewelry you would like to wear. Obviously your main choices are rings, earrings, bracelets, and necklaces. A full set would include all of these but you may not prefer to wear some of these types of jewelry. For example, I have never been much of a bracelet person. I will wear them when the occasion warrants it but overall I find them to cumbersome and to get in the way. You may have similar opinions about other types of jewelry. So before you decide which types of homemade jewelry you are going to make to finish out your ensemble you need to think through what you like to wear.
Next, you need to consider the occasion you might be wearing this jewelry too. Mainly you need to think about whether or not this is a formal occasion or it is one that is more casual. This will play into a whole array of things when it comes to designing and making your new jewelry. If this is not for a specific occasion then you can merely consider your general tastes and preferences and the types of events you usually attend.
Finally you must consider your outfit. You need to think about a lot of things about your outfit but you mainly need to consider style and color. When it comes to style you need to once again consider whether it is a formal or casual outfit. Then when it comes to color you want a good blend. You do not want to match the exact same color of jewelry to the color of the outfit as you risk people not even noticing what you have created. But you also do not want the colors to be terribly mismatched or your jewelry and outfit will clash. You just want a good blend that brings a balance of attention to your jewelry, your outfit, and of course you.