Bulk strings is the way to go. I provide therapy music several times a week and change my strings frequently. Bulk works for me.
It’s way cheaper to buy bulk packs of strings than buying ready made sets. Get exactly the thicknesses you want, too. I buy these, and have my husband install them.
I've been using these strings, bulk packed, for years. 12 in a bag. Cheap price, highest quality. I use both the ball end and loop end strings.