In games of pure luck (roulette) maths is a more or less a waste of time long term - you are going to lose in the long term, maths can help you find the game where you will lose your money more slowly, or allow you to have strategies that allow you to lose more slowly.
In games where skill is involved, then maths can be your friend (but also your enemy).
For example, in sports betting (requires lots of skill), understanding the following mathematical concepts can make a big difference, some of them are 100% necessary:
- what do prices reperesent (e.g. 3.0 = 33.3% chance of something happening)
- staking (how much should you stake on each bet)
- statistical modelling sports events using past data (a h-u-g-e subject)
Poker is another good example, but the maths is relatively straightforward to learn - everyone just learns the same maths (probabilities) and pot payout calculations. Poker is so much psychology as well (yuk!).
Of course, managing your own psychology is ANOTHER super-important part of long-term winning in gambling. But without some good understanding of the maths... you are probably getting nowhere.