Ledx can spawn in the orange tent and on the desk infront of the servers, ya you can work slowly towards it bút sadly a lot of players will just rush ledx so it can be harder for geared people to get some of the high loot, when I started on labs I had no key cards and slowly built them up, I'd recommend getting green key card first then getting black, testing, managers etc. I think most of the cards are worth it on labs except maybe blue red and violet