I've never done the shuttles so I can't really provide any detail on them, but if you haven't located this link to your shuttle options, then here they are:
https://www.renoairport.com/tofrom-airport/shuttlesBasically there's a limo service, a North Lake shuttle and a South Lake Shuttle. The South Lake shuttle is like $30 per person. You may not need a rental car if you're staying in South Lake. It is much more dense and there's lots of entertainment within walking distance from any of the South Lake casinos. If you are going to the north shore, the communities are much less dense and you will likely want a car to get around.
Another option is just to Uber. The current price for an Uber from my office in Reno to the Hardrock Casino in South Lake is $80.