A flyball set... at least $100 and no more than $300

And an agility set will cost $600 to $1000

Good luck, and here is somewhere you can get some agility equiptment:

http://www.affordableagility.com/

And Flyball equiptment...

http://www.flyballequip.com/flyballequipment.htm

You can get information about agility and classes here...

http://www.agilityfun.com

EDIT: Agility classes usually cost $50-$100