On day 3 you get the 'ante up' mission within which you have the option to play some strip poker in the safe house with Jack and a seemingly random selection of other survivors.

Alas I seem to consistantly get delivered absolutely rubbish hands and I've found the absolutely outstanding Ultimate Trainer alas does not change the cash available during the poker game, only the regular gameplay cash level (understandable).

So my question is, how the devil do you beat these people?
I'm guessing I need to find some gambling books or something? Where would such things be found (I've only found combat mags so far).
Or if all else fails, what would be the odds of getting a trainer targetting the ante-up cash reserve?

Braaaaaaaaains...

Gambling Magazine 1: Ragazines (second floor of Royal Flush Plaza - R212)
Gambling Magazine 2: Stan's Large Print Books and Magazines (second floor of Palisades Mall - P206)
Gambling Magazine 3: Shamrock Casino (first floor on the Silver Strip - H106)
Credits to Xive

Wow that actually helps a ton. Do you need to have all three with you or just read them for the boost?

You only get the bonuses from magazines if they're currently in your inventory. They're shared between players in co-op as long as one player has the magazine in question.