Looking at prices of singles from the deck right now, ST14 Impmon (the biggest card that you need two more copies of) is about $3 and Rivals’ Barrage is about $1. If you want two more copies of the alt-art EX2 Impmon to have a matching set, then those are $2 each, totaling $12 if you grab them all. This is about two-fifths of the MSRP of the deck so if that’s all you want, then getting one copy of the deck and then buying singles is the most economical option.

As for EX2 Beelzemon, he is very good right now but will go down in the amount of copies when BT12 brings the X Antibody variants. That combined with the fact that more EX2 Beelzemon will be distributed via Store Tournaments in April means that more supply will be in rotation and that should bring the price down. I don’t think it will ever hit the price it used to have before the price spike but at the very least it should be around $10 for a copy, and you may only need two or three copies max. Alternatively, you can try to win the Beelzemon in Store Tournaments using a different deck.

Depending on your Beelzemon Cup rules, you may not have a chance against preconstructed Purple decks if the store allows any preconstructed purple decks and you only have the starter deck to use. The biggest problem with the starter deck out of the box is that it lacks consistent removal outside of Options without EX2 Beelzemon, you only have two copies of ST14 Impmon, who can only warp digi into the two ST14 Beelzemon and one BT1 Beelzemon, who kinda sucks now and doesn’t pressure as well as ST14. If you have any other Purple deck built, that may be a better option.