While there are various strategies and betting systems that some people believe can give them an edge, the reality is that the outcome of each spin is random and independent of previous spins. As a result, it is generally not possible to consistently beat the roulette wheel in the long run.
But is wishing for 4 stars to max them in genshin, gambling: YES, it is gambling. Because you can use all your money and not even get a single 4 star you wanted. The same goes with standard banner characters. The thing of notice in here is Pity system.