Layering looks effortless and then you spend the whole evening pulling two chains apart. The fix is mostly about length and weight, not luck.
Leave two inches between lengths
Chains tangle when they sit close enough to swing into each other. Two inches of difference between each piece gives every chain its own lane. A 16 inch choker, an 18 inch mid length and a 22 inch longline will stay separate through a normal day. One inch apart will not.
Put the heaviest chain at the bottom
Weight settles. If the thickest chain is your shortest one, it sits high and the lighter pieces slide underneath it. Reverse that. The long chain carries the most weight, the short one is the finest, and gravity keeps the stack in order for you.
Mix link shapes, not just lengths
Two chains with the same link pattern catch on each other. A flat snake chain next to a rolo or a box chain slides instead of gripping. This is the difference between a stack that survives a coat going on and off and one that does not.
Mixing metals is fine
Gold tone and white gold tone in the same stack reads as deliberate when the lengths are clearly different. It reads as an accident when the pieces are almost the same length. Commit to the gap and the mix looks intentional.
Storing them
Most tangling happens in a drawer, not on a neck. Clasp each chain closed before you put it away and lay it flat rather than dropping it in a dish. An unclasped chain will find its way through every other loop in the box overnight.
If a knot does form
Lay the chain flat, put a drop of oil on the knot, and work it apart with two straight pins pushing outward rather than pulling the ends. Pulling the ends tightens it. Stainless steel is forgiving here, but the pins do the work, not force.