Hey,
Im Cypher, a Gold Player from EUW, i've always enjoyed playing Jungle, especially Vi, i carried myself out of Silver with Vi and i noticed she is a very powerful Jungler and even better ganker. I discovered a nice Soloqueue Build, please notice that this Build is pretty aggressive and NOT recommended for Rankedteam games!

High Damage
Shreds a Tank's Armor in seconds
May Carry a game easily
Great Engages and Teamfight potential
Kills Enemy ADC in seconds
Can't get kited

Easy to play but hard to master
Her early game isn't as good as other Junglers Early (e.g. Udyr)
Has no escape after engage
Team reliant in the Lategame
Needs to hit Q to deal the most damage

At first: Feel free to change the Ruznes, you can change the Quints for 9%AS+MS and the Marks for Flat AD.

Flat Armor will make us more resistant when ganking and in the early Jungle, MR per Level will give us the needed Ammount of MR to Tank a few Skills casted by the enemies Mage.
The Reason why i chose to mix Apen with AD is easy: Its the most powerful Combination of AD Runes all the way, lets do some Maths and take Xin Zhao and MF as an example:

Assume you as Xin Zhao, have 9 Armor pen marks and 3 armor pen quints, this would give you a total of 25 armor pen((9*1,66)+(3*3,33))
Xin Zhao his base attack damage is 56 + 3,1 per lvl
So you run up to Miss Fortune who has a base armor of 15(assuming she has no items/ masteries/ armor runes)and start auto attacking her, her armor will be lowered by your current armor pen, so 15-25 = 0 armor(seeing as armor pen cannot make armor negative) so that would be 10 armor pen you don't need at that level.
so xin deals true damage at lvl 1 to MF
Xin deal 59 damage to MF at lvl 1

When xin and MF are both lvl 6:
Xin has 25 armor pen and 56+(3.1*6) =75 Attack damage.
MF has 15 base armor + 3 per lvl so 15+18 = 33 armor
to calculate how much damage xin would do we need this formula : 100 / (100 + Armor) to know how much damage MF's armor will absorb. so MF's 33 armor - Xin's 25 armor pen = 8 armor left.
100/(100+8) = 0,93. so MF's armor absorbs only 7% of xin's attack damage. 75-((75*7)/100) = 70.
so xin would deal 70 damage to MF with his auto attack.

if they're both lvl 12
xin armor pen = 25. xin AD = 56+(3,1*12)=93
MF's armor = 15+(3*12) = 51
51 -25 = 26 armor
100/(100+26) = 0,79..thus 21% of incoming damage is absorbed. 93-((93*21)/100) = 73
Xin would deal 73 damage to MF

If they're both lvl 18
Xin's armor pen = 25. Xin AD = 56+(3,1*18)=112
MF's armor = 15+(3*18)=69
69- 25 = 44 armor
100/(100+44) = 0,69.. thus 31 % of incoming damage is absorbed. 112-((112*31)/100)=77
Xin would deal 77 damage to MF


Now lets take a look when Xin would have all AD marks and all AD quints. giving Xin an additional 15 AD. but no armor pen

If they're both lvl 1
Xin's AD = 56+(3,1*1)+15 = 74
MF's armor = 15+(3*1) = 18 armor
100/(100+18) = 0,85. Thus 15% of incoming damage is absorbed. 74-((74*15)/100)=63
Xin would deal 63 damage to MF

if they're both lvl 6
Xin's AD 56+(3,1*6)+15= 90
MF's armor = 15+(3*6) = 33
100/(100+33) = 0,75 thus 25% of incoming damage is absorbed. 90-((90*25)/100)=68
Xin would deal 68 damage to MF

If they're both lvl 12
Xin's AD 56+(3,1*12)+15 = 108
MF's armor = 15+(3*12) = 51
100/(100+51) = 0,66 thus 34% of all incoming damage is absorbed. 108-((108*34)/100)=71
Xin would deal 71 damage to MF

If they're both lvl 18
Xin's AD 56+(3,1*18)+15=127
MF's armor = 15+(3*18)=69
100/(100+69)=0,59 thus 41% of all incoming damage is absorbed. 127-((127*41)/100)=75
Xin would deal 75 damage to MF

Lets take a look at our Runes: 6 armor pen marks, 3 AD marks and 3 AD quints. giving xin 10armor pen and 10 AD

If they're both lvl 1
Xin's AD 56+(3,1*1)+10=69
MF's armor = 15+(3*1) = 18 armor
18-10= 8armor
100/(100+8)=0,93 thus 7% of all incoming damage is absorbed. 69-((69*7)/100)=64
Xin would deal 64 damage to MF

If they're both lvl 6
Xin's AD 56+(3,1*6)+10 = 85
MF's armor = 15+(3*6) = 33
33-10=23 armor
100/(100+23)=0,81. thus 19% of all incoming damage is abosrbed. 85-((85*19)/100)=69
Xin would deal 69 damage to MF

If they're both lvl 12
Xin's AD 56+(3,1*12)+10=103
MF's armor = 15+(3*12) = 51
51-10 = 41 armor
100/(100+41)=0,71. thus 29% of all incoming damage is absorbed. 103-((103*29)/100)=73
Xin would deal 73 damage to MF

If they're both lvl 18
Xin's AD 56+(3,1*18)+10=122
MF's armor = 15+(3*18)=69
69-10=59 armor
100/(100+59)=0,63. thus 37% of all incoming damage is absorbed.122-((122*37)/100)=77
Xin would deal 77 damage to MF

so this is what we get :

...................Full armor pen..................Full AD........................Hybrid
Lvl1:.....................59..............................63................................64
Lvl6:.....................70..............................68................................69
Lvl12:...................73..............................71................................73
Lvl18:...................77..............................75................................77

We want to get our Jungleitem as fast as possible and even though Devourer became very popular since 5.12 we want to take the AD Item, The APen and the CDR is very useful in early levels and you can gank more often because you dont have to farm jungle creeps 24/7 to get your Devourer stacks up. Afterwards we will take a pair of Boots and build Phage asap, this provides survivability and some Extradamage and faster Clear, we will now take a lookat our enemy team, are there more ADS or APS and how strong are they, if there are more AP's, take trinity and mercurys, if there are more ADS, go for the BC to stay alive longer and shred their armor because more ad means more bruisers means more enemy Armor to shred. You can combine this with the BOTRK to have some great 1v1's, you may Rush this after BC or get Randuin first, remember: more AD doesnt mean you should take Ninja Tabi, if they are CC Heavy and AD keep your mercurys because of the Tenacitybonus. If the enemy has alot AoE Dmg (e.g. Kennen, Zyra, Orianna, Malphite, Amumu) That scales with AP, you need to take Locket! Take Banshees at the end to engage faster so you cant be stopped during your Q-Engage, thats pretty important for Teamfights! Always try to ULT the most dangerous enemy (usually ADC or Assassin or Nuke Mid) If the enemy has alot of AS you can take a Frozen Heart and combine it with the Thornmall, take Righteous Glory if the enemies are having a high rate of mobility so you are quicker and do a successfull hard hitting engage, you should not take the Spirit Visage since you haven't got any Selfhealing and only for the BotrK is noot worth it. Remember to always take a Pinkward with you, its very Effective to clear Baron or Dragon or just to remove enemy Wards at the Lanes or everywhere else, use your Trinket to support your support at Warding.

Its Very important to take some early Dragons, if you take it early you can take it multiple times and more often, After having the first part of your Jungleitem and 2 Longswords or better the whole item plus 2 Pots and a vision ward (lv 5) you can take him down, he will take half of your HP, make sure to clear all wards and make sure taht the enemy jungler isnt near!, always look at the Dragontimer and do it ASAP, the Dreagon supports your team very Well!

Thanks for noticing my first Guide, i will make it more Colorful and fill it with Pictures when i have time, i will try to keep it up-to-date.

Have Fun!