>>83384661A case pretty much guarantees you an SSP and a handful of SPs. Weiss is a strange card game economy since any singular booster box you find second hand will 99% of the time be "dead" as in the SPs and SSPs were already fished out of the case it came from. Getting them straight from the HoloFes stand or convention booth has pretty high odds though of being live. I also think bushiroad rigs those boxes a bit anyway, since they're kinda clowns like that.
Weiss is also a game that pretty much no matter where you play it, JP cards are accepted. I personally have trouble deck building if most of my cards are in JP though since I have to constantly reference longer effects. The general deck building itself can be pretty simple since a good chunk of your deck is decided for you with 8 Climaxes and 6-9 Climax combo cards, then you just build around those colors and synergies. NePoLaBo is pretty simple since they're all designed to work off each other.
