How to get to Riwwi, Coliseum of Games
In order for you to get to Riwwi, Coliseum of Games you'll first need to make it to Natimbi, The Broken Shores. To reach Natimbi what you'll need to do is find a Magus (there's one in the Guild Lobby as well as at every LDoN camp) and say Nedaria to them after hailing them. If you need help locating a Magus, head over to my How to get to Natimbi Guide for more information.
Once you're in Natimbi you will want to go to the north-central most portion of the zone which is where you will find Qinimi. From the Qinimi zone line you will find Riwwi to the southwest, it's rather straight forward getting there.