Hey there! Vegas local here!
Look up Tix4Tonight, they usually have discounted tickets for shows that night, so no advance notice needed. However, you're not necessarily going to find the shows you want on there all the time.
Non-locals don't tend to get any deals for anything since you're tourists and they want ALL your money.
Also, look into the My Vegas Slots app. Its a free slots app where you can earn fake currency to redeem real world products such as show tickets, room discounts and food comps. I've used it a couple times and its really cool! Best thing, I haven't spent a dime on it.