Mercury Sigil/Crest....Help

[mj05]

i was just playing for a sec and noticed that if you get off the airship at Sanubia Desert, you're stuck. I didnt know you had to get off the ship at Bikanel Island and then go north for it to be considered Sanubia. lol Im gonna try to do this quest. I noticed that i have time limits for anywhere b/w 10 and 15 seconds when i was looking at that guide. Is it easy or hard to reach those limits?

Edit~Ok, thanx for the help. I found the cactuar stone. and about 4-5 of the cactuars. (and the crest). One question, tho...do I have to actually win a certain number of times to get the Sigil? Because I've only won twice so far. Im not sure if it matters what kind of sphere you put in the stone.