How to use:
Start with Mercury Cannon
1)Open gate and quickly shoot enemy
2)Hyper Charge
3)Mercury Hammer
4)To the Skies! and while in mid air, lightning field
5)Activate Youmuu's Ghostblade
6)AA, AA, AA
7)Thundering Blow
8)Mercury Canon
9)Open gate and shoot
Results: You're faster (20%), with increased AS for around 5 more seconds, your enemy is slowed (40%) and has been thrown away from melee range. Basicly enemy is dead and your hardly scratched

Need attack damage, not speed, since skills will benifit most from this. For the same reason, cool down reduction and armor penetrations are nice. At the same time, you are tanky.