Lots of people have been asking where to get the gambling magazines, many only say 2 of them, but there is indeed a third, but its quite harder to get than the other 2, also this really helps raking in money from the big slot machine in Slot Ranch Casino, and the 2 Poker missions.
Gambling Magazine 1: Palisades Mall on the second floor of the Bar Grotto thing in the middle of the mall, its on top of a table near the water slide.
Gambling Magazine 2: In Americana Casino on the second floor of the BBQ Shack.
Gambling Magazine 3: To the RIGHT of the ENTRANCE to Hotel Fortune City there's a platform you climb, there you'll find some stuff and a safety deposit box KEY, PICK UP the key then go to Uranus Zone, once in Uranus Zone go to the BANK and into the VAULT, then find the Safety Deposit Box Number and use the key to get the 3rd magazine. (If you found any other keys you'll also be able to use them here to get money or some gems and stuff)
Also, wear the Sports Fan outfit, and be sure to wear the WHOLE outfit to get the gambling perks, it also helps with getting money from the big slot machines in Slot Ranch Casino and beating the 2 Poker Missions!