Elise works really well as an AD bruiser top. I've been very successful with her like that from early to late-mid game (haven't had a game last long enough to comment on late/extreme late game).
They way I build her is:
AD red+quints, armour yellow, mr/lvl blues
Standard 21/9/0 AD masteries
lvl.1 - Q
lvl.2 - E to allow for early ganks / escape
lvl.3 - Q
lvl.4 - W
lvl.1 boots + 3 pots
first b - 1Dorans blade + phage or heart of gold or 2 dorans blade (depending on gold). Always get wards
from that point onwards, focus getting a Phage > Frozen mallet > Frozen heart or Raduin's (I usually go Frozen heart for cdr, armour and mana)
Boots are dependant on their team. Likely to go for Merc boots or Ninja tabi but could go sorc to help with damage or mobility if you want to roam loads (which is really fun as her)
From this point onwards it's really dependant on how you're doing against their team. Could want a bloodthirster, could want an infinite edge, could go tanky. Looking at the new Black Cleaver, that could be worth it to get too
The reason why this works without having to go for much damage is that her Q damage scales with their level due to the % damage, so allowing you to become a really tanky, but still deadly, bruiser.
If you make good use of both her forms in team and solo fights, you can poke them down pretty fast in human form and then initiate with E (in either form, preferably human and then use spider E to chase if they flash or such) to finish them off in spider form.
With the minor damage bonuses with this latest patch, it might be worthwhile going more ap with things like the Hextech gunblade (maybe? it is expensive..), Guinsoo's Rageblade, but currently she works so well as an AD bruiser that I'm having issues thinking of ways to cost effectively incorporate AP into her