I would start be purchasing 5 good counseling games including:
Totika (which is counseling Jenga and has various decks of cards i.e., self-esteem, divorce)Therapeutic/Counseling Dominoes Game Set (there are 7 - I like the Anger Control the best)
Talking, Feeling, Doing game
Face It! Feeling cards
I would buy a silent timer, markers and colored pencils, dry erase markers and some small white boards, art paper, and a few fidget toys.
I love books but they are expensive and you can borrow them from school library, interlibrary loan, and some are available free online.
All counselors need a locked space to store confidential information but hopefully the school would provide this.