-Skarner has enough sustain after your first jungle run (where you should be around level 4-5 depending on if you have ganked)to be able to easily go through the jungle without the need from the extra creep damage from Hunters Machete.
-Doesn't build into anything Skarner really needs, because after say 10-12 minutes into the game, you won't be spending much time in the jungle.

-Good Magic Resist, helps mitigate damage.
-Tenacity is really useful as Skarner is a 'in your face' type of champion and needs to be able to disengage quickly or keep up the chase.

-Its slow passive helps keep foes in place and has good synergy with Crystal Slash.
-Health.
-Attack Speed helps maximise Skarner's passive.
-The passive from Sheen helps increase damage.
-Good damage.
-Movement speed helps close gaps.

-Amazing amount of Health for durability
-health regen is always useful.

-Again attack speed maximises Skarners' passive damage output
-Magic resist mitigates damage
-Wits End passive helps AP champions do more damage.

-Armor helps mitigate damage from AD attacks
-Good amount of health
-Active keeps enemies locked down.

-All these work well with Skarner and are just suggestions to help with your situation.

-Defense, Skarner need the durability.
-The anti crowd control masteries really help skarner disengage or chase down enemies.
-Defender works well as skarner will be in the thick of it in every team fight.
-Utility, movement speed help skarner move around the jungle quickly at the start of the game.
-Offense, Cooldown reduction allows skarner to kep his crystal slash going and his shield on cooldown for as little time as possible.