Ramblin' Gambler achievement

Need 1) Read 14 Gambling Jack books. 2) Get 21 in Black Jack. 3) 4 of a Kind or better in Poker

Summary

As the description says, to get Ramblin' Gambler achievement, you need:
1) Read all 14 Gambling Jack books.
2) Get 21 in Black Jack.
3) 4 of a kind or better in Poker

7-7-7 in Slot machine doesn't count. No idea about roulette.

I've got the achievement myself, but I simply write this short guide summarizing what other people found out in the Discussion so the next person doesn't have to dig through it and I don't see any guide summarizing this.

Yes, getting 4 of a kind is hard. No real trick I've found, except that holding one card has a better chance than changing all card. Here's my moment: