An example of whichever used as a pronoun is in the sentence, "She can pick whichever," which means she can pick any one from multiple options.
Read whichever books you please. It's a long trip whichever road you take.
He may choose whichever desk he likes.
An example of whichever used as an adjective is in the sentence, "She may go to whichever place she likes," which means that she may go to any place she wants.
Whichever car she buys, she'll be in debt.
He may choose whichever he likes.
Whichever he chooses, he'll be satisfied.