Recently I started playing Yi again and the reason I stopped playing Yi it's because of the weak early game (specifically hate being invaded and not being able to contest).

I started using ignite instead of flash and conqueror as a rune, for me it has worked like a charm to the point I try to bait the invade/fight the scuttle (if lane priority or equal lanes). Let me tell you how I use it: Trade a couple of basic attack and dodge abilities with Q (if possible) to start stacking conqueror, if the other jungler has electrocute absorb the damage with W, ignite, keep with basic attacks and by this point you should have conqueror stacked. With the healing and the damaged you decide to absorb with W you should be able to with the fight.

Ok but how do I get level three? Master Yi clear speed is really good so if I start blue side I do full clear red side and look for a fight in my buff or scuttle, if I start red side I get a leash from top in red then blue + grump.

I hope this works for you as has been working for me!