What ever economic plugin you are using should have a option in the configs to give new players money. if not, then you can always be crafty and make it were only new players spawn in a room and they hit a button that goes to 2 command blocks, 1 that gives them money, and the other gets them away from the button they they cant press it multiple times. now with killing players I'm not sure. you can try browsing plugins that have something that will help you. good luck!