Less popular usually means cheaper action, so on the strip I would try Circus Circus, Casino Royale, and Excalibur.

Also note that every casino changes the minimum bets by time of day, so in the evening when things are jumping the minimums go up, even at less popular casinos. For lower bets go in the morning or midday when things are slow.

If you don't mind going slightly off strip, you can get the free shuttle from Harrah's to Rio, and then walk next door to Gold Coast which has a reputation of being the casino that locals patronize.