I think there's not an actual answer for that, it really depends on your track and what you're aiming for. If the final result sound muddy and crowded is because there's too much layers or because you haven't mixed them properly (sometimes both xD) so my advice is to make sure those layers you have are really adding something to the track, if not, just remove them.
Also, adding a ton of elements doesn't really mean your track won't be repetitive, try to use the same sounds in different ways to keep the song interesting.
Thats it I guess