Heh not really, the cheapest to get them *immediatly* is through the "Booster packs" (99.5 cents/card), otherwise it's to get the 50 tickets and wait for the girls to get on "special" (100 cents/card). Technically you can get all of them for that price since when you buy one a new one comes in the empty slot. It's, imho, a bit long though.
Once up to date on the cards, there's normally 7 new cards per week unless some major problem occurs (which they tend to fix up during the week anyway) so the recommended method would then be the 6 month subscription (~33.16 cents/card). I'd do this before actually purchasing tickets since you get 10 of them on your first subscription. [Edit] For sakes of completeness, the "newbie" booster pack comes down to ~82.916 cents/card.