It's a shame about the chance cards, but like any other chance card, you take your chances and see what the outcome is without really knowing what you are doing. Quite apt considering it's a casino career.
I really like this career and recommend it to anyone who wants a really highly paying job. Other than the poker tables, it is a shame there are not any gambling/casino objects available for TS2. I have vague and fond memories of the slot machine from TS1 where being miserable gave you a higher chance of winning.