Definitely check out the guide then, it can sort of get you into the swing of things if you haven't already. If you don't have a 3* or 4*, you should work towards that, and they're easy to get without spending money on a box.
And yeah, compared to other iOS games (which is what I play), $30 is a lot
of money. It's really essentially similar to gambling, so consider if you're all right with that first before doing anything.
As for your question -- events typically introduced limited edition rewards, and there are often limited edition series that come out at the same time (for example Armed Forces & Venus Colosseum, last big event was Demon's Tower which also had Dark Elves series). In a sense, these are limited edition. However Fantasica came out in Japan first (and is months ahead of where we are here in the English version) and at one point they had a "reprint gacha" (aka reprint boxes) that included all previous limited edition cards up until then. So they're not completely
gone forever, but it'll be awhile.