When I was in the aryths spire mirror maze, I read this map but I dont know what it means,
Which is the starting place?

where you start is random, I believe?
The map just tells you what the two options in each room leads to (make sure you read all the textboxes so you know what room colour you are in)

So if you're in the Silver room, taking the Left mirror will take you to the Amethyst room, and taking the Right mirror will take you to the Sapphire room.
if you're in the Jade room, left will go to Emerald, Right will go to Amethyst
from Amethyst room, left goes to Emerald, Right goes to Sapphire
etc.

So you want to get to Garnet and go right to Ruby, left to Gold, and then you can get to the boss, but if you went left from garnet you'd end up in Sapphire, and if you went right in Ruby, you'd end up in Emerald

If my memories are good the first time you enter you are on the emerald floor, it have been a while for me tho so it may have changed/i may recall wrong. This shoudn't affect anything if you have already tryed / explored the maze on your own before looking at the map, pay attention on what is said on the color of the floor next change and look at the map to know what miror to go next. ^-^