@saintlydevilisit's a good idea to play multiples of some of the cards in your deck. You have the right idea, for sure. That said, how many is all dependant on the deck you're running and cost of the cards. For example, it's almost always a good idea to run four bananasaurus when that is your closing card, but you really shouldn't ever need more than two of, say, cornucopia. Also, try to include cards that have extra value when played, cards draw being Paramount. The more card draw you have, the better your chance of getting to those cards you need. If you'd like, you can post the decks you like running (and it would be really helpful to post your available cards with them) and we can help you tighten them up a bit.
As for the event cards. The ones that cost 2k were only available for sale. They weren't part of an event (from my understanding). That said, they are also exceptionally powerful cards. Most of the ones that cost 2k could easily be legendaries (not all, but cards like leprechaun and zombology teacher, definitely), so while 2k is a lot (and the recycle value is a joke), it's actually a pretty good cost, depending in the card.
@jakeman102201 i don't think that any of the cards themselves need an actual nerf. i think that untrickable itself needs a nerf. if a card is untrickable, that should be it's value, it shouldn't be able to recieve benefit from friendly tricks either. and again... i'd really like to see a silence effect added to this game. with the direction it's headed, eventually there will have to be minions and tricks that can remove lasting effects from other cards. i think either one of these would do wonders for the game without throwing off the balance.
while i do find that the game is balanced at the higher levels of play, i understand how frustrating it can be when you just don't have the cards available to you to take on the threats that the game is throwing at you when new sets launch. i think these changes can help bring more balance back to the game all the way through the ranks without really nerfing any cards along the way, or making them less viable at higher levels of play.