I made this Starlight Rose farming guide to help out players who want to farm the herbs instead of buying them from the Auction House.
You can pick this Herb from skill 1, you will get the same number of herbs as if you had Herbalism 100, but gathering Starlight Rose will often still fail and you will only get [Starlight Rosedust]. This doesn't depend on your herbalism skill, it's just the way this herb was designed.
One of the new features in World of Warcraft Legion is that herbs have ranks now. You can get the new ranks from quest items that you get by picking [Starlight Rose]. Once you finish the quest you get from the herb and the follow up quest, you will get the new rank.
Rank 1 : Attempting to gather a starlight rose will fail less often.
Rank 2 : You can get [Blood of Sargeras] when gathering Starlight Rose.
Rank 3 : Attempting to gather a starlight rose will always succeed.
Starlight Rose
Get these three items to speed up farming: [Leystone Hoofplates], [Demonsteel Stirrups], [Stonehide Leather Barding].
If you have the 
[Sky Golem] mount, you can use that instead of the Demonsteel Stirrups, and if your class has a tanking spec, you should switch to that while farming, so you won't get dazed and you don't have to use Stonehide Leather Barding.
Don't forget to enchant your gloves with 
[Enchant Gloves - Legion Herbalism]! This enchant brings gathering time down from 1.5 seconds to 0.5 seconds. This is really important if you gather while mounted, because mobs can still interrupt your casting.
Suramar
Pretty easy to follow route, but it takes a few laps until you learn how to avoid most mobs. Withered Hungerer can spawn while you gather this herb, and you should always kill them snince they drop 4-6 Starlight Rose.
You can turn off 
[Mana Divining Stone] by right clicking on the buff. I usually turn it off because it's really annoying while farming.
This route is for players without flying mount. (If you barely find any herb, it means someone is already farming there.)
If you have flying mount and use the recommended enchants above, you might farm too fast and you need to take a bigger loop around the zone to allow the herbs to respawn. So use this map below:
