Recruit - 0
Grunt - 50
Drone - 100
Jackal - 200
Brute - 500
Hunter - 1000
Elite - 2000
Prophet - 5000
You might next wish to ask what the Forum Ranks/Titles do or earn you. Well, nothing really. The forum ranks are just a little system to reward members who are active and engaged with other members. The addition of the contributions to Trophy Points from giving and receiving "likes" was the primary reason we decided to utilize the Forum Title/Rank feature of the new forum software. Because the title is based on more than just post count, but on giving and receiving likes from other members, it is a means to encourage people to be active with other members and their threads, instead of staying insular to their own posts and threads.
Your next question might be why they are Covenant names. We chose to name them after the Covenant races, over some other suggestions, for three reasons. One, we felt it might be considered by some to be disrespectful to give people "Military Titles" like Private, Colonel, Sargent, and so on when we are just a fictitious costuming group, not a real military unit. Two, we thought it might be confusing to some people to have their Forum title based off of a UNSC unit, like Marine/ODST/SPARTAN-I, -II, -III, -IV, and so on if that was not the costume they were doing or had done. If you made an ODST, but your Forum rank was SPARTAN-II, you might think something is wrong, or it doesn't reflect your costume. Finally, we wanted to do our best to showcase and include all aspects of the Halo Universe as a reminder that while the majority of our members do UNSC costumes, we are a costuming group for all members of the Halo World, and encourage and include Covenant costumes among us.