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From the Beta, only your first gold star public event of the day counted toward you getting a reward. All the others you received your own satisfaction of finishing. On Earth explore, the Devil Walker would spawn in the Divide every half hour at the top and bottom of the hour. Pretty easy to be doing some pvp or checking out the tower and know that you can quickly head to old russia and take this guy down pretty easy and there were always at least 5 other people in this area to help so you weren't alone in trying.
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Xur is going to be your extra reasoning to rank up your cryptarch and find as many public events as possible. I received 4 coins from each of those during the beta. His prices are speculated to be from 7 to 9 coins for each piece of gear. Seems low as I was able to build my collection up in less than 12 hours in game.