The letter y is tricky indeed. It can make many sounds, more than three!
Yes, y is a consonant in yellow and yolk.
Sometimes y makes a short i sound like in system and gym.
A y at the end can a vowel be, with the sound of a long i or e. How do you know which you see? At the end of one syllable words, y often says “i” like in fly. With more syllables, it is often a long e.
There are some exceptions, like the one syllable word “key” with the long e sound. (Hey! No Way! -ey can sound like a long a in some words like grey, and the vowel team -ay a long a will say.) You can’t deny y is long i in two syllable words like: July, supply, reply, rely, and apply. Some two syllable words go in the long i pile like typist and style.
WATCH videos and PLAY online games about Tricky y at the Vowels That Vary Wakelet tutorial.
Practice Tricky Y with a story and word sort at my Teachers Pay Teachers Store.