You have to get the Iron Banner faction to rank 1(100 points). One way is to rank it up is to win 5 games in the Iron Banner crucible matches (20 points each). Remember to get bounties since those will also give you faction points. I was able to get the Warlock band in the knick of time for completing a bounty where I had to get 20 melee kills. I did it one mach and the bounty gave 100 influence points.

Just do some missions and the strike and I think you should be all good, but I hear you have to be level one rank on the Iron Banner though.