I am limited on play time but I manage to get minimum 2 alexandrite per day and here is how. I don't know how often your server "hunts" but Mateus is pretty active. I use Ariyala's hunt tracking website to see how many hunts are up or close to being up. If hunts are up I join a group and farm the A & S ranks for as long as I can. This usually nets me 200+ Allied Seals and Soldiery which equals 1 Alexandrite and 1/2 of a map. Once the hunts are thinning out, it is getting close to the end of my time, or no one is hunting I pick up the daily alexandrite map quest and run my ex roulette. I know it's not instantly gratifying but I can get 5 or more every 2 days only having 2-3 hours of play time per night.