Early-Game

You usually want to focus on farming, preferably single target camps such as red buff, blue buff and gromp / crab. Unlike many other junglers who tend to be in meta usually, You don't have a very strong lvl 2 gank, so if your opponent jungler does, make sure to inform your team about it. If enemy laner, preferably mid has something very immobile such as Orianna and hard matchup such as ignite LeBlanc, lvl 2 is an exception where just burn flash for flasdh and make life of your laner easier. On the other side, you do have a very strong dragon and herald take. You can even rush the dragon at spawn (5min) which is what you usually want to do with Vi if the opponent jungler is not around. Make sure to go for herald as well, especially before 14min, through Herald you can take first tower break or just give a nice bunch of gold to your laner very easily (keep in mind plates falling off).
If you are maxing Q which is the path you wanna go for most of the times, you have to keep in mind that enemy can dodge it and you will lose most of the damage and the very important CC/aftershock (if you run this oldschool rune choice) proc as well. Therefore, ganking from flank or bush, etc. positions from which enemy does not have as much time to react to you as if you just walked up to him, is rather the prefered way.
You can also do a Q flash, try it out in practice tool, speaking from experience, it's very useful at obvious ganks when enemy is able to react with their flash to you and also if you miss your Q in a situation where you should not be missing it, you can make up for it with the flash trick.

Conqueror keystone

Ideal keystone for bruisers, even more after the durability patch.

Lethal-tempo keystone

Possible alternative for bruisers, I personally don't like it but can be nice especially if you utilize vs very tanky enemies by also going something like BOTRK.

Aftershock keystone

OLDSCHOOL: Aftershock used to be ideal keystone for Vi, Old reasoning: because of her R being reliable way to use it, howerver, you prefer to get Aftershock proc with your Q to proc it immediately as you arrive to the fight. It is a weaker in terms of damage dealing than other keystones, but gives you a massive ammount of tankiness. Be careful before lvl 6, if you miss your Q, you are basically fighting without a keystone.

Using ultimate

You can use your ultimate as a damage source in combat.
You can use your ultimate to pick a single member in the fight and lock him down, using R on someone then Q, after you land on his head, keeps him at a place for quite a long time, which can be lethal especially against squishy carry champions. Be careful of enemy Morgana / Spellshield champions.
You can use your ultimate to zone enemy from your fed carries and create as much chaos in the fight with sacrificing yourself as possible.