Depends on your workflow, the result you want and the amount of processing you use, and thousands of other variables. I don't see why you want want to use the number of layers in a track as a usefull 'aim'.

Also; About getting rid of the crowdiness. Use as little layers as possible, but as many as needed. EQ everything properly and give it its own space in the L/R and stereo field. Layering synths with different textures reduces the amount of layers you need and can create new textures.

Right now my song has around 60, but I'm not even close to done. I want to keep my track constantly changing so the listener doesn't get bored, and the only way to do that is by adding new elements at certain points. It could be something as small as a click or as big as a new melody. I usually add in a bunch of random things that I think will sound cool and then cut some of the bad stuff out until I get what I want. Just remember that you shouldn't be adding anything to your song if it doesn't serve a purpose. For every single element in your track, you should be able to explain to yourself why you put it in there.

There is no right amount of layers, you just have to make it fit perfectly ofcourse.

This makes me think of a screen of one of madeon's tracks:

Hmm.. for me it's anywhere from 40 - 100. To avoid crowdedness I mute everything down to the kick. Then I unmute one layer at a time, starting from the sub bass and so on, only unmuting another layer when I'm completely done processing the previous one until nothing sounds muddy or crowded.

Honestly, as many as it takes, but I would say there are a few base layers that a lot of finished songs would have.

Lead - For melodies
Chord - For chords (duh)
Drums - For rhythm
Vocals - For added meaning
Bass - For groove

And sometimes:
Sub - For speaker-rattling

Those are some very common layers that most songs would probably have, but almost all music is made about as differently as the people who are making it. Just do what feels natural, you shouldn't really have a set number to go by. Make it with as many (or as few) layers as you see adequate.

It really depends on you! sometimes you can make a song with just 20 layers sometimes up to 100! it really depends on how it sounds and if it sounds complete for you

I usually end up around 50 tracks in my song. But a finished song should have the amount of tracks it requires. If you want to reduce stuff in your projects you can try bouncing down certain groups of stuff into audio but at the end of the day, it really doesn't matter (As long as it's not eating up your CPU. But you probably don't have 50 elements going at once and it's spread throughout the project anyways ).