I recommend to buy some different loads and figure out what the gun likes and will cycle reliably.
I usually look for the best value, lowest velocity loads the gun will cycle.
1140-1200 fps
My favorites are the Remington Gun Club Target Loads #7.5 shot.
For slugs I like Fiocchi low recoil slugs in the yellow or black box.
Test at least a couple boxes of each shell before you buy a bunch.
Test them with the gun clean, as well as filthy dirty.
You don't wanna run em with a clean gun, only to find out the loads choke after a few hundred rounds.
Remington Gun Club Loads
Looks like Dicks has free shipping, not sure if there are exclusions for ammo though.