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If you want to be money wise. I would suggest renting for as cheaply as you can and wait for Chaos Legion to release as its likely (not gntd) that CL cards will cost less then the current ones. From what I been reading most renters like to rent on the last day of the season and run up their account to the highest league they can for max rewards. If you time your last day of season renting correctly you will be able to use the rented cards on the first day of the following seasons as well.