The secret to layering is made up of two rules. Simplicity and space.
1) Stick with fine delicate simple pieces. If you want a bold statement look stick to a single big necklace and a chunkier style.
2) Necklace length is important! Don’t layer 3 18” necklaces for example, they’ll just overlap and look messy on the neckline and totally go against the look you’re going for!
My favourite look with layering is to have a fine gold choker (important that it’s super fine and delicate or it can just look a bit much when layering with other pieces) a 16 or 18” necklace as my “mid” piece, then a longer one at say 20-24 inches. These sizes will create space between each piece, giving you that perfect layered look.