My question is: Do you spend the money you gain with the service you are working for?
Most of the time, yes, but sometimes I don't. Sometimes I prioritize buying something else with my paycheck from my signature campaign rather than gambling with it. I occasionally gamble my earnings when I have spare and when I'm in the mood of gambling.
It depends upon the campaign requirement. Some gambling campaigns require their participants to gamble as a part of their rule.
Been doing signatures campaign for almost 3 years and I never encountered something like this rule, maybe you are referring on sites that are giving free balance which in order to withdraw you need to wager 10x the value of it. Having this kind of rule will surely kill your campaign (if such a rule really exists).