You can have up to four of any card, such as creatures and spells, in your deck
While I try to avoid giving ridiculously low offers in an actual negotiation (just putting an offer out there knowing that you'll walk if it's rejected is not negotiating), it's always best to aim a little bit under the price you are will to pay to give yourself some room to up the offer
By my estimation (and I don't value cosmetics highly) the Spark Bundle nets you a positive $15 in value , the key is if the 1,500 gems are worth about $10, and the wildcards are worth a combined $30, then you minus 25 ($24.99) from 40 ($30+$10) to get the $15 in value
Seeing as Commander players start with 40 life, Dark Confidants life-sapping abilities are somewhat mitigated, but players should still watch out for taking too much damage
This transition is at the heart of the game's dynamism