Elise is awesome. While she definitely is viable at other positions, based on the few games I've played with her I believe she belongs in the jungle. Here are two theory-crafted guides that I've been thinking about for sometime now that 'should' work when jungling Elise.

The glyphs, seals are standard jungler stuff, marks are for the fact she is an ap assassin and needs the dmg, but the quints you have a few options:
Ability Power to pack a punch early game, and help you clear the jungle quicker.
Flat HP for early game survivability.
Spellvamp for survivability throughout the game.

These Masteries seemed to fit her best. Comment opinions.

Explanations to come.

Although one thing, I believe there is room for a youmuu's ghostblade somewhere in build, with an early blade of avarice for gp5, still figuring it out though.

Max Q for more dmg and leap for those ganks.
Next W for atk speed buff and homing spider, great dmg output and jungle clear times with these.
Finally E because all it gives when you lvl it up is lower cooldown by a fairly insignificant amount, so do it last.
And obv lvl R whenever possible.

Flash Smite. You could substitute Flash for something else, but Flash is op and allows greater mobility in numerous situations.