Go to Zandalar and find any “WANTED” quests. Those all give pretty significant 7th legion rep. Then any world quest in Zandalar, any world quest in a warfront in the explore status will give 7th legion rep. Not much per, but they build up pretty quick.
If you just did the warfront quest for the loot, that means in about a week, Arathi will be on patrol status for Alliance. There are 5 WQs daily in the patrol zone, each rewarding 7L rep, service medals, and either gold/AP/war resources. I think it’s 75 rep each, so daily thats 375 rep you can easily get while it’s on patrol, which is about 6 days.
You also get big chunks of 7th Legion/Hornorbound rep for: the island expedition weekly, Incursions (incursions to the opposite continent give 7th Legion while local incursions are split between 7th Legion and the zones faction), and completing the warfront siege quest that gives you a piece of gear.
I’m back from the front and it appears that I was mistaken. Completing Warfront: The Battle for Stromgarde gave no reputation, simply completing the warfront likewise gave none.