OK, managed to vote now. It cost me 1 xpr each vote and I need a negative and a positive vote. So its 2 xpr cost per couple of votes.
So I need 4 xpr to spend each day to use all my votes.

But I don't understand the incentive still.

I already have 350 + 350 votes from all the previous days. The daily rewards from the total of all these votes are very small. Less than xpr each day.
Why should I spend my 1000 xpr to vote when votes return so little? I will never gain that back.

Also I don't understand what is the point of owning cards. They don't seem to give me any reward. Or is it that when people vote on my cards I get their vote money?

Is there a place that explains all these things in detail?