The best way to recruit really depends on what you want out of the recruitment system, but if you want to do A>B>C>D>E, then you should wrap it around and close the circle with A>B>C>D>E>A, so that all of the accounts receive all of the benefits.
As for cost, you can upgrade any trial at 50% off by simply creating a character on it, and the next time you log into that account you'll be prompted to upgrade to a battlechest for 50% off. For the expansion, I've not familiar with any sales at the moment, and I doubt there will be until late November/early December.
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