For me, what i did was i just spammed daily challenges and weekly and just did Firefight Arcade ALOT, but it payed off :D.
There is no easy way, but it is possible. Just play alot of games online and spend as little as possible, and you will eventually reach any number of credits that you want.
Play the game, a lot.
Completing challenges
An easy way to get cR (Credits) in Halo Reach is to go on Multiplayer Matchmaking and choosing "Score Attack". You are the only one playing, and you get a lot of cR. You can also choose the maps and games to want to play on. Have fun with that.
Play a lot and a LOT of matchmaking! Or hacking but I do not recommend that because you will be banned and nobody likes a hacker.
It is unlocked at the rank of Colonel on Halo: Reach and costs 1,200 CR
Inheritor You must have 20,000,000 Cr.
Hack Halo reach or what I do leave my xbox on and my spartan safe place to get endurance points
by playing campaign, firefight, or matchmaking
not anymore
205000 CR
No but the XP you get in Beta will still be on the normal Halo: Reach but you will not keep the Armor or cR
tatical soft case 100000 cr
Mark V Helmet - Lt. Colonel, 130,000 cR Helmet Upgrades for Mark V - CNM - Lt. Colonel, 10,000 cR UA - Lt. Colonel, 15,000 cR Mark V Shoulders - Left - Brigadier, 100,000 cR Right - Brigadier, 80,000 cR Mark VI Helmet - Brigadier, 300,000 cR Shoulders- FC-I[2] - Brigadier, 75,000 cR UA/HUL-I - Brigadier, 75,000 cR
The Commando helmet in Halo: Reach is unlocked at the rank of Commander (600,000 total cR and +60,000 from the previous rank which is Lt. Colonel Grade 3). It costs 85,000 cR