The number of ropes you need depends on the workshop, so always check the event description first.

Some numbers that I found that work are:

4 ropes = beginners set
8 ropes = intermediate set
12 ropes = advanced set
15 ropes = you have elevated to the supreme level 🙂

Having a few shorter pieces rope in your rope-kit can come in handy, ie. 2m and 4m.

Suspension work generally requires more rope than floor work.