I have seen a lot of people who take Vi top lane. I just feel like it doesn't do her justice to go top when she has such an easy time clearing the jungle and ganking lanes. This guide will focus solely on her jungle gameplay and ganking methods.

For my masteries I go 21/9/0. Going nearly straight down the offense tree from Fury to Executioner , I only stop to put point into Havoc , Butcher , and Destruction . The purpose of this is to maximize damage in all the things Vi is good at. Mainly, beating on creeps, backdooring towers, and assassinating champs that are low on health.
In the defense tree I take Tough Skin / Bladed Armor and Durability / Veteran's Scars . I put my last point into Hardiness to take a slight edge off of the damage creeps do.

Putting the right runes on Vi is really important. I feel like she fills the tanky dps role in the jungle, using her auto attacks to put out maximum damage while her Blast Shield absorbs as much as possible.
I take Mark of Attack Speed and Glyph of Attack Speed so I can get my Denting Blows of as many times as possible thus putting out maximum damage. Some people may feel running armor runes on her is better, be my guest, but personally I believe that attack speed is what makes her really efficient in the jungle.
For my seals I take Seal of Scaling Health. This allows her to come out of the jungle far more tanky than expected. I guarantee you that when that Ezreal down bottom sees you coming with 1,000 health by level 4 he is going to think twice before picking on your ADC too much.
Finally for my quints I take Quint of Armor Penetration. This will allow you to shatter even more armor than you are already.

Putting summoner spells on Vi is relatively easy. I chose Flash and Smite for very good reasons. Flash will allow me to pull off my ganks more often, give me escapes, and allow me to secure kills when they flash out of Cease and Desist's range. Smite on the other hand, is because I am jungling. It is pretty straight forward. You use smite to finish off that first Ancient Golem and from then on to secure Dragon and Baron Nashor.

I take Denting Blows at level one to help me with Ancient Golem. It helps you bring him down extra fast while taking minimum damage. I actually max it last though, I take Relentless Force at level two, maxing it first to clear camps and create a steady/reliable damage output. I max Vault Breaker second, it helps me get off ganks better, speed up my jungle, and put out a bit of extra damage. With Cease and Desist you should take it at levels 6, 11, and 16, as you should with all ultimates.

I open the game with a Long Sword and two Health Potions. This allows me to put out some extra damage. Once you go through the jungle, and maybe pull of a successful gank or two, you should have enough gold to buy your Vampiric Scepter and Boots. These will allow you to jungle endlessly.
After a little bit of saving you should go back and buy a Recurve Bow which will allow you to apply the most stacks of Denting Blows in the shortest amount of time. Still, you need to be careful... until you back this next time. You now buy a Phage, though it seems like a small purchase, it gives you enough health and damage combined with it's passive that you are a force to be truly reckoned with.
Now that you are slightly tanky, you have been able to tower dive, duel, and secure some kills. What will you do with all that extra gold? Buy a Wit's End and Mercury's Treads. They will allow you to stomp mid lane and take their tower. While you aren't invincible, you sure aren't easy to kill.
With your next bit of gold you should build into your Frozen Mallet. This will make you fathoms more tanky and let you slow 100% of the time instead of the 25% chance. You should be able to secure many more kills for your ADC and mid lane which will earn you assists. Assists mean money, and you know what money means!
Start on building your Tiamat. Until recently, the Tiamat was frowned upon in competitive use. Now with the addition of Ravenous Hydra the Tiamat is no longer considered "trolling". So what should you do? Obviously build Ravenous Hydra!
Next build your Avarice Blade, with your new AoE auto attacks you should be raking in the gold by the truck load. Finish your Atma's Impaler for the extra armor and damage and then buy a Hexdrinker to hold your last slot. Chances are the game didn't make it this far... but if it has you can build that Hexdrinker into the Maw of Malmortius. This will complete your build and turn you into an unstoppable force.

(Note: If the team is AD heavy and you are having trouble sticking in team fights or staying alive, you can always build a Guardian Angel. While I am not the biggest fan of GA on Vi, sometimes it is necessary.)

In the jungle I start at the Ancient Golem (Blue). You don't NEED help here, but it is always nice to get a few hits in from a buddy. Smite it. You then move directly to Wolves. The Wolf camp should be super easy, as should be your next stop: Wraith camp. By the time you get to the Lizard Elder your smite isn't up yet. So I actually recommend going to Golems and taking them out first. After that you can run up to Lizard Elder and land some Denting Blows/ Relentless Force before you Smite him. After you get Red I recommend ganking bottom or mid lane. If your team doesn't need you immediately you should keep farming to level 6. Gank immediately after you get Cease and Desist.

Vi is not an extremely good farmer early in the game, that is why she is good in the jungle. She has to get close to last hit, her Relentless Force isn't a reliable wave clear, and it can be really hard to aim. Late game however, she gets her Tiamat/ Ravenous Hydra and will demolish any wave of minions sent her way.

Vi lives up to her reputation as a vigilante cop. She can handle herself and she don't need no man to help her. But, she is EXTREMELY good at helping other people. Oddly enough, Caitlyn seems to be the best ADC she could ask to gank for. Yordle Snap Trap and Ace in the Hole combined with Cease and Desist and Vault Breaker is one of the most terrifying things I have ever seen in all of League of Legends. Coincidence? I think not.

Pros:

Steady Damage Output
Gap Closers
Built in Shield
Armor Penetration

Cons:

No Built in Sustain
Not the Best Initiator

Vi is a very solid champion. She has a nice spot in the current meta and can fit well into most teams. She can either make you or break you though. If you feed her when she is your enemy she will make your life miserable. But if you feed her while she is on your team, you will never have to worry about that carry that is hiding in the back of enemy lines ever again.