Clearing the live a 100 times might seem exhausting, but you can autoplay live shows after completing them once, which means the CPU will do most of the work for you.
Then there is the green skip tickets, which you can obtain from completing missions and are given as daily bonuses as well. They skip the live show completely and give you the item rewards at the end. This counts as a clear as well.
But you need to obtain an S rank score on a specific song, before you can use the green skip tickets on it.