Experiences can get more rich and varied.
Experiences can get richer and more varied.
Thanks in advance
I tend to agree with Mr. Bhaisahab if we're speaking of grammar in its strict sense. However, I disagree that it sounds wrong. We might well refer to something as "rich and varied" almost as if it were a single concept (similarly to "bread and butter.") Since that is the case, I would not consider the first sentence to be incorrect.
To elaborate in an unnecessary way, I might say that a trip to Rome would be "rich and varied." "Yes," you might reply. "But if we added Florence it would be still more rich and varied."
Again, I would prefer the second sentence would accept the first.