What is in a juggling kit?

That depends very much on who you're buying from, and how much they're charging. The kits can range anywhere from three low quality beanbags (often found at your local novelty store) to a wide range of props (some kits include a diabolo, three balls, a spinning plate, clubs, and an instructional DVD).

The bottom line: ask whoever is trying to sell you the kit. There are many kits available online that may give you a baseline expectation to work off of.