Karma Booster
level up a character to level 38 give you a choice of karma booster so use your birthday scrolls and level up tomes on a key char up to 40 each week net you 2 black lion keys from story and a karma booster.
Here’s a list of ways to increase Karma gain:
https://wiki.guildwars2.com/wiki/Karma#Karma_modifiers
Good luck.