BPhillipYork : Well this definitely will lead to a horde of creatures and has some potential with other "cares about outlaw effects", most of the Assassins you'd really want to copy are legendary sadly
As its not only able to search all Karakuri monsters, even themself, but also Karakuri spell and trap cards
You should find a deck to work towards - you'll probably find one of these online thanks to the huge selection of pre-built decks that have been uploaded and can be downloaded freely - of course, you can only actually build and use these decks if you own all of the necessary cards
Sword Coast Sailor and Raised by Giants are two options that broaden your access to other colors and make for some quick kills via commander damage.
Completing missions, participating in events, and scrapping duplicate cards will award you with Shinedust, which can be used to trade with other players online, potentially helping you collect cards that you aren't lucky enough to get from packs
They are too expensive for one Secret Lair set by themselves, that would be something like $60+ of cards even in nonfoil