As Repete says the match director should be sending out a note indicating the totals of each that are required.
Naturally you should bring about 1.5 times what is suggested so you do not run out should you have a reshoot.
A few more suggestions as well.
For Slugs try to get the low recoil ones. I use S&B slugs that come in a box of 25 that are nice and soft as well as being relatively cheap. (less than $1 a shot). If you buy hunting slugs you will be a hurting unit after a long stage of slugs. Barrie had one last year that was 26 slugs or something like it. Shooting 1550 fps slugs was a challenge to say the least.
For steel and clay you use birdshot, I use off the shelf 7 1/2 trap loads.