At the very beginning of the Dagger, and buy a health potion, if we play map 5 vs 5 and we're on the right side, I would recommend to go to the top, if we have a tank in the team to ask him to go with you (If this character who has a stun eg Sion it's better for us) If we start the left side, I recommend to go to the bot.
If we play 3 vs. 3 map does not go to the top only on the bot (Low recommend walking alone on the top if we are confident that our opponent is someone not only on the small range atack.

I have so much to say about the Master YI If you liked this build let me +:)