It's very simple, ordinary gamblers will know the limits they need to follow, they will not go beyond those limits and when the limits are reached, they will stop gambling because they know they have already exhausted either the time or the budget they had allocated for their gambling activities.
Addicted gamblers know no limit, they don't know when they need to stop gambling even if they have crossed their limits or everything, when they exhaust their current balance, they deposit more if they have, and if they don't have, they will try to get some money from here and there so that they can gamble with it.
So, I don't think there are any differences between the two that one shouldn't be able to differentiate between the two types of gamblers.
The thing with an addict is that, they lack the basic functionality of control or knowing limits since what got them into addictions in the first place is the lack of that limited control and that is also what different an ordinary gambler from an addict, sometimes an addict will sell they properties and even homes just to gamble it away with the hope of recovery and even when they make good winning, there still will put everything into it and becoming sucked in it to the extent that they become uncontrollable.
But an ordinary gambler, will already have a set part to follow and he have principles and guidelines that will help him along the way and also be able to keep him safe from the possibility of getting into such problems.