Get anything, random good IVs are extremely hard to get and It won´t be EV trained correctly, so get any treecko now and breed it with a modest or timid ditto (holding Everstone) to frontier. It will save your time and natures aren´t SO important in-game.
Then you ask me, Why? here´s the answer:
Personally, I'd recommend Modest or Timid for in-game, probably Timid over Modest for the Battle Frontier. DO NOT use Brave or any other nature that reduces Special Attack or Speed; those are Sceptile's strengths. I would also recommend that you consider rebreeding at some point to get Crunch onto a Sceptile (breed with Bagon/Shelgon/Salamence) as Modest/Timid Sceptile with Leaf Blade/Dragon Claw/Crunch/Thunderpunch is quite strong.
A) You can´t get bagon before E4
B) You can´t get Move tutor who teaches T-punch Before E4
C) Dragon claw is a good move to be wasted in a pokémon un-ev trained with bad IVs.