Points wise, these cards only make sense if any fees on the card are less than the value of the points earned and no other problems are created.
As far as spend goes, if you have a job where you put travel on your credit card and get reimbursed later, your CC spend will probably be higher than if you have to spend your own money.
Others have found ways to push more day to day spend through credit cards. Look at each transaction in your checkbook and determine if there's a way to use a credit card instead of a check in a way that makes sense; using your CC shouldn't cost more[1]. Then as time goes on, you look at each credit card transaction and decide which credit card to put it on for best results. For the points game, don't carry a balance. Paying interest wipes out the value of the points.
There are a number of threads already here on getting spend up. Proceed rationally, and ensure that any method fits your needs. Not all will.
[1] If you are trying to make a spend goal, then it can make sense to lose a few dollars on the individual transaction in order to make a spend goal and get 25K-50K points for doing so. But outside of this, paying to push the rent or mortgage payment through an intermediate to get 1000 points is almost always not a good deal.