Kha'Zix top skill/evolve order..

i dont get tear. Max W evolve W for sustain/damage/dueling/safe farming

It's based on what you need in the game at that time.

Generally speaking though, the power curve on evolved Q doesn't pick up until mid to late game anymore as opposed to how it used to just be a flat out damage increase last season, so you can safely avoid that one... especially with how the isolation mechanic is harder to trigger now.

Upgrading his W gives a wider AoE with more damage, a better slow, and correct me if I'm wrong but I believe it also increases the heal.

Upgrading his E doubles the range of his leap and refreshes the cooldown on kill or assist, letting you hop about as you please.

Most say to upgrade either the W or the E first. I haven't played him in the new jungle yet, but last season I was a fan of upgrading his E first for the increase to my ganking potential and mobility. However, in the new jungle sustain seems to be ruling so upgrading his W might be the safer bet to clear the jungler at a higher health percentage, then take his E, then evolve his Q.

Don't evolve his ult. It's been nerfed all to hell, doesn't even allow him to gain resistances while it's active, and is essentially good just for slowing enemies and dealing a LITTLE more damage since it'll let you proc Unseen twice in one duel against someone, three times if you count the initial moment you strike them after moving through the fog of war. If you happen to trigger the event with an enemy Rengar and get that final evolution point, go crazy and enjoy yourself. Otherwise leave it alone.