You're Probably Layering Your Necklaces Wrong
Tip #1 Your Shortest Necklace Is Your Foundation
Everyone has a certain necklace length that's most flattering, so it's important to test a few lengths and see which one works best for you, Once you have that base, think of it as the foundation on which you can layer up.
You can keep it 2 inches apart for something more subtle, or go super long with the second length for a dramatic look, any way you go, having that foundation is always the start.
Tip #2 Less Is More
You'll want to stick to no more than 3 here. Anything more than that might be overdoing it.
Tip #3 Chain Type and Placement Matter
When layering three necklaces, you want the attention to go to the top necklace and the bottom necklace, adding that the middle necklace should be something clean and simple. If you choose to include only one pendant, go for the bottom.
Tip #4 Add a Pop of Color
If you've gone for a neutral or strictly monochromatic look with your clothing, adding a vibrant pendant necklace or chain can serve as the pop of color you're missing. As for where in the stack said color should lie, focusing on the shorter chain because it's the closest to your face, and therefore can highlight some of your features.
Also, you might want to incorporate just a hint of color when layering necklaces, in order to "keep things from looking too busy" . It will also make any stones seem more expensive if there is only one. Less is more here.
Tip #5 Experiment with Shapes
When layering pendants with different shapes, pay attention to how the shapes work together. Layering a pendant with a chain necklace is an easy way to get around that. Make the chain more of a choker with the pendant hanging down long or keep the pendant up high with a more bold chain around. This is a great way to freshen up a pendant or chain you've been wearing for years.
Tip #6 Rock the Look with Loungewear
Layered necklaces can upgrade an otherwise 'lazy' look. For example, if you're lounging in sweats, pulling a few necklaces together with a clean pair of studs is the perfect combination to take your comfy attire up a notch.
For a crewneck or V-neck, mixing chains with pendants to draw more attention to your jewelry than your outfit, while a crisp pullover calls for doubling elegant chains.