The $25 slot machine in the Buffalo Head Casino nets you a higher than average number of Bars, Watermelons and 7's when you spin, making it particularly lucractive.
Get at least $100,000 or more to get the Laurel Palace (Caesars Palace). The easiest way to do this is go to the 2020 casino and keep playing $500 Slot Machines. If you get more money save your game and if you lose, you can re-load the game. This also goes for the GameBoy version.