Classic Skarner Guide - from a Chronoshift veteran

This is the typical jungler start. The potions are quite needed and handy even after your first clear.

One option is to swap out one health potion for a mana potion as a hedge if you somehow lose your first blue buff.

Ancient Golem is Skarner's core first item, improving jungle clear, health, tenacity, and sustain for faster farming and stronger early fights.

Ninja Tabi are usually the best boots, though CDR Boots or Mobility Boots can be good in certain games.

After Golem, build a Sheen for more damage and just sit on it. No need to upgrade it yet necessarily. Runic Bulwark is a very efficient item that Skarner is great using. You can build Sheen into TriForce if you are very fed.

After your core, round out your build with tank items based on the game. For MR, Spirit Visage is best if you want to reach 40% CDR, while Force of Nature offers more MR and valuable movement speed. For armor, Randuin's Omen is the standard choice thanks to its durability and active. Frozen Heart is great if you still need CDR, but avoid overcapping it. Thornmail is a solid option against fed auto attackers but prioritize Randuin's.