ok...you're bronze V....which basically means you want to keep it as simple as possible. That's not an insult...it's a simple matter of concentrating on the core basics and mastering those will help you improve and grow. Do not worry about invades...do not worry about counter jungling during the laning phase.
The strongest jungler in your arsenal is 
and it's not even close. Get her down...period. Kha'Zix and Fiddle are decent...those should probably be your fall backs. You dont' want to over do it...keep it to three junglers that you know and know well. 
is terrible because he can be kited like it's nobody's business...however he is amazingly strong, especially in lower ELO...so feel free to keep him as a pocket pick...but I would definitely make your number 1.
With you want to start your W, and then E and then Q. After that...max your Q first followed by your W. (Honestly Vi is so versatile you could almost max any of them first depending on what you want...W helps your farm, Q helps your ganks). Vi is incredibly strong post level 3...so feel free to gank early. Never gank a losing lane, look for lanes that are over extended into your territory and ping your players so they know you're coming. Don't over pursue...getting a blown flash is all you need as it allows you to come back anytime in the next 5 minutes for an easy kill.
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When to counter jungle? Remember to always tab to check your timers...if you just regrabbed your red...chances are the enemies red is spawning/spawned (assuming you know that you both started the same jungle route...easy to tell by the type of jungler your enemy has). If you just grabbed red...and you're wandering toward mid and the enemy jungler shows bot...grab his red or grab his raptors, etc. Never counter without vision. Buying wards is important...so if you enter the enemies jungle...have a ward handy and plant that sucker deep in their jungle to provide you and your teammates vision.
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Double jungle....don't do it...period.
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Invades aren't worth it...especially in Bronze V. You invade for 2 reasons...one...to get some deep wards early so you know where people are starting...or 2...your 5 v 5 early game is superior. Most people have no clue if they're stronger overall level 1. It's best to just do a standard mid field lineup. AKA...people all run toward river and stand there waiting to see if someone pops up....drop a ward at about 1 min, then head back to their start positions. Again...at your ELO you want to keep things as simple as possible to master the basics. Concentrate on farming and neutral objective control/warding.
With Vi I generally run AD marks, armor seals, MR/18 glyphs (cool down isn't bad) and attack speed quints.
You need to remember...the most important thing you can do as a jungler is farm. Farm, farm, farm. If you don't constantly farm your jungle you'll get too low in levels and the monsters will never level up. Everytime the monsters spawn, they spawn at higher levels gaining you more xp. If no lanes show ganking potential...farm.
Remember to ward...I know a lot of people don't understand it and think it's a waste of money...it's not. If you have 75 gold...buy a ward. If you're running a yellow trinket...upgrade it at level 9 for 250 gold...it will give you 2 wards like a mini-sight stone. When dragon is going to spawn in over a minute...start heading down...begin to ward around so that you can get vision on the area.
Good luck...Jungle ain't easy. Just remember to keep it simple and concentrate on the core things. Farming...you know you're farming ok if you can stay within a level of your solo lanes. Never gank a lost lane...concentrate on the lanes that are neutral/winning. Remember that a blown flash is a kill later on. Return to those lanes.
(still learning),
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I also own 
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Hook will mean certain death for an enemy if your support can land it and you all pile in. Also
binding works well too... IF you didn't get a kill or you don't think you can steal the buff call it off and start your jungle route.
