I wanted to create this guide because I read other guides that are very helpful, but didn't agree with my style of play with Elise. I wanted to put this out there for others that may play like or similar to this style of play. I use Elise as a very aggressive Mid Lane or Top Lane. She pairs with just about anyone, but a strong melee I think is best for Top or Solo Top/Mid. In this guide I will describe what I think Elise's best attacks are and how to use her with this build.

First off Skill Sequence. This is were she can be difficult to master but very fun to play.1. Neurotoxin/Venomous Bite Neurotoxin is your main attack to provide damage while in lane. Venomous Bite is your kill attack while in spider form. I choose these attacks to level first after acquiring VS/SF and Stun/Leap.2.VS/SF Volatile Spiderling/Skittering Frenzy. VS really doesn't do mass amounts of damage, but the chase factor it has can sure annoy anyone in your lane. I like to use this when a Champ is sitting by a turret, drop VS and watch it run right to them. It is also great for taking out groups of minions 3 or 4 at a time if they are low on HP. SF is your main damage dealer while in Spider form. This ability is very important. You need to keep your Spiderlings alive for maximum effect. @18 having 5 Spiderlings significantly magnifies your damage out put. SF while zip threw enemy HP and finish with a Venomous Bite.2.Cocoon/RappelThese abilities are last to be leveled they don't do any damage, yet can cause massive amounts of damage to be done, hence these 2 abilities are your most important, I think. The cool-downs are long so use wisely and Cocoon eats Mana early game. Mastering these 2 abilities will be your greatest ally with Elise. Cocoon is a stun and can be used several different ways, save your butt with a stun escape, save a teammate, gap closer for damage attacks, etc.... Rappel is your main gap closer or can be escape. It removes you from combat so enemies may focus on someone else. You can steal say Baron, or Blue/Red buffs. Hide out an attack over a wall. Several options here also.
Attack RotationThis is were you need to master Elise and her capabilities. Like I said in the Inro, I like to play her aggressive, but this can get you into trouble. You need to learn to stay alive, 3+ deaths early game your screwed very hard to make up. No deaths is ideal but stuff happens. Ok now the attacks.
Once I have all 6 abilities is when the fun starts.
Spider Form will be main for clearing minions and then offense and defense. I start by using Neurotoxin to beat the enemy down, swap form Rappel to close, SF then VB. If they are still alive and running swap form to human, Cocoon, VS and finish with Neurotoxin. If they happen to be alive they are probably by a turret or running home. If you close and use SF to VB and they want to stay and fight I still like to either flash away or move away and hit Cocoon, VS, and Neurotoxin on them. By this time your Spider Form should be off CD and switch back and lead with VB your SF should still be on CD but close to being open. Rinse repeat. Try to think Assassin, Rappel on your victims and shred them with Spider Form attacks, swap forms and finish them off or Cocoon to escape and swap back to spider for enhanced armor/protection. Kill Steal is the idea. I hate to put it that way, but Elise is squishy, she can't go head to head with big bruisers or heavy Melee until late game. 5 spiderling SF and VB will kill just about anyone. Or start on a tank with Neurotoxin, VS and Cocoon, swap close with Rappel SF and VB to finish. Elise takes time to master. She is a very fun champ to play.

I have played around with different builds, from jungle to full AP, and other hybrids. For this style, My style of play, I find these items work very well, but are not set in stone. I start off withBoots of speed always, and 3 health pots. I sometimes start with Cloth Armor and 4 health pots but very rarely, cause that's usually my 3 item purchase. The Cloth Armor helps mainly cause I use Spider Form and can take a few more hits with it early game.Sorcerers Shoes, easy to acquire early usually my first purchase. These are easy to get in Mid Lane early on. Great for Neurotoxin, Magic Pen. early game really helps out Malady, is important to get early on, by mid game, you can hold off on this if your having issues with bruisers, I sometimes opt to getGlacial Shroud, one for CD reduction and the armor boost. But still like Malady first, it really adds to your Damage output for Spider Form. Glacial Shroud lowers your CD's which is crucial for your Spider Form attacks. Getting an SF w/5 spiderlings and 2 VB's in one strike most opponents can't with stand such a brutal attack. Next is Rylais Crystal Scepter. This item increases your Human Form attacks which aid in assisting your Spider Form abilities. AP doesn't scale well with Elise, but is necessary to do the proper damage. This item also has slow, who doesn't love that. Now your late game items can very, this all depends on what the enemy is building and who their champs are. I like to get Lich Bane, paired with Rylais, is deadly combo. Use your Human Form attacks and pop into spider the added 100% of your Ability Power in damage to your VB or SF attacks is deadly awesome. And increased movement to chase them down. If needed go for Sheen then get an AP boost from a different item such as Void Staff or Abyssal Scepter for Armor/Resistance or Rabadons Deathcap just more AP then finish your Lich Bane. Late Game items can be totally dependent on who your enemy is, what they are building and how your team/you are doing. I like Void Staff for more Magic Pen. always great in late game especially against tanks.

Pros

Able to get early game kills
Can gank other lanes when possible dependent on Rappel/Cocoon
Fun to play
Multi lane capabilities Mid/Solo Top/Bot
6 abilities(If CDs are managed several attacks and be carried out very quickly)
Late game rocks potential for high Kill numbers and assists.
Great team fighter

Cons

Can be difficult to play, once you master her abilities this really isn't the case
Squishy, very dependent on not dieing early.(this goes for most champs though)
Very mana heavy for Human abilities(Used wisely this isn't a problem)
CD management can be a problem for some.(If your on CD stay away from combat)
Again squishy.(Pick your fights wisely, don't try to be a hero will result in free kills for the enemy)