What are Map Bonuses?
When you complete events on the map, you get the rewards in sequential order. It’s not a 100% chance, but it’s pretty high.
It’s not based on chance. You get progress based on your event participation, with gold giving you 50% of the next reward.
Thanks for the clarification, I thought it might be something like that.
The wiki does actually have a reasonable amount of detail. Just posting the link here in case you hadn’t seen the page?
http://wiki.guildwars2.com/wiki/Map_bonus_reward