could always use this site to give your ideas and get your ideas from http://leagueoflegends.wikia.com/wiki/Vi/Strategy
when I think of how to play a champion, I like to break down the stats that they'll want as core, are nice bonus, and what I want to avoid.
Needs: (core stats you should focus on)
Hp - shes an initiator and bruiser, all her attacks are either melee or will put her in melee range. she'll be easily targeted by the enemy and thus will need to be able to survive the inital volly of attacks. Also because of her high AD ratios, she'll also dish out a ton of damage, making you a threatening opponent and can make teams want to focus fire on you. this will also increase that inital blast shield she will get thus helping you survive better.
Resistance - both armor and magic will need to be taken into consideration, like I mentioned with hp, your gonna be in the front lines, you gotta protect yourself and make sure you survive that inital volly, this will help you do just that.
AD - all of her abilities scales with AD, and they scale very well. because of this you wont need so much AD to dish out a ton of damage, but if you can get an item with AD and defensive stats on it, then its a good chance its a must have.
Armor pen - like I said all abilities and her damage is Physical thus makes most sense that this stat is a must have to further multiply her damage output.
Cooldown Reduction - Originally I thought this wouldnt be such a great stat to get since 2 out of her 4 abilities would be affected by it, but I was wrong. now knowing that it also reduces your excessive force charge time, this becomes a very useful stat. if you get the 40% cap, you will now have cooldowns of 4.8 on Vault breaker, 4.8 on Excessive force and 48 seconds on assault and battery. this means that you can jump in with vault breaker and hit your combo, and if need be, you can jump back out with vault breaker for an escape. and you'll be able to use exessive force quite often to up your damage.
Wants: (stats that you dont need to focus on but if it has a "need" stat then its a great bonus)
Attack speed - most people will think attack speed should be a must have since denting blows procs after x amount of attacks, and if her attack speed is higher, she'll proc it more often, but really it depends on how you play her, I believe shes a combo fighter, where she does her damage based on her combo and after it is done, she should get back, leaving very little to auto attacking. especially in the early game when your defenses arent as strong yet.
Lifesteal - majority of her damage isnt going to be coming from her auto attacks, but instead will be coming from her abilities, because of this, you wont gain much from lifesteal. though if the item provides other stats that will help out, such as blade of the ruined king, then it shouldnt be ignored.
mana - the mana consumption on her abilities arent all that high and you wont be spamming her abilities as often as you'd think, since you should pick your times to harass instead of just mindlessly spamming. though more mana does mean you can keep the harass going for a longer period of time. just not really a stat to go out of your way to get or if you have to think of what part of an item to buy first, buy the other.
Movement speed - this stat will be helpful to keep stuck to your opponent but since shes got 2 gap closers and 1 being on a fairly low cooldown especially with cooldown reduction, you wont really need this as much, but you shouldnt avoid it. get it if the other stats are great buffs to vi.
Donts: stats to avoid
Magic pen - this is just pointless since all of her abilities do physical damage, there is no magical damage on her unless you get on hit weapons besides blade of the ruined king. just no point in getting this stat at all.
AP - she only has 1 ability that scales with AP. since everything else scales with AD, it would make more sense to go with AD instead. try to avoid this stat as much as possible.
Crit chance/damage - like I mentioned before, majority of her damage comes from her abilities, thus they wont gain any benefit from crits since they wont be able to crit. avoiding this stat is best.
so heres some items I feel should be core to her
Frozen mallet - this giving tons of health and a slow to stick to your enemies will be a great boon to her offensive power while giving her a great chance to survive that inital volley
or Iceborn Gauntlets - the spellblade passive will give her a great amount of aoe damage a long with an aoe slow giving her a chance to use excessive force to everyone affected. also provides a good amount of mana and cooldown reduction to allow more casts. though I wouldnt get both this and frozen mallet since they both provide similar utility. though it wouldnt be the end of the world if you had both.
I would get iceborn gauntlets if you were against a heavy physical team and frozen mallet if against a heavy ap team.
black cleaver - just all around great on her. every stat on this item is something that she needs, and thus becomes a core item for her.
some very good situational items
Randuin's Omen - since your the initiator, chances are the enemy will attack you at least once, this will cause them to take the reduce attack speed and movement speed giving your team a chance to survive, also providing a ton of health. though only get this if the enemy team has a few autoattacking champions, if they're mainly AD casters and AP champions, you might want to look into a different armor such as Sunfire cape.
Mercurial Scimitar - since Vi is such a melee oriented champion, she can be kited fairly easily once both vault breaker and assault and battery are used up. this will help you keep in the game and also provide you a good boost in AD. also a decent amount of MR.
Maw of Malmortius - This will be the must get item if your opponents are heavily in magic damage, this will help negate a large amount of damage, also since you have your blast shield, you can survive fairly well even at low healths to take advantage of the extra AD from missing health.
Blade of the ruined king - if you really want the life steal then this is the item you should get, this will help you gain a 3rd gap closer and also help your team out since the active not only slows your opponent but also speeds you up as well. also great against tanky champions who build heavily into health.
Ravenous Hydra - though im not a fan of lifesteal on her, but with the massive amount of AD this weapon would be great on her if your opponents are mostly melee or short ranged, meaning they will end up grouping up and you'll be able to hit them for a ton of damage. dont even bother with this item if team fights are fairly spread out.
as for boots.
I would get either merc treds, ninja tabi, or Ionian Boots of Lucidity, Swiftness and mobility arent really needed on her since her ability to harass is so high that she wont need to roam and can stay in lane.
as for enchantment i'd go for captain all the time. you should be the initiator in every fight thus the person in the front line and you'll be able to drag your team along with you to every team fight. and once you dash in, you'll want to have your team in the fight as soon as possible. with all the gap closers you have, you wont need alacrity's extra movement speed to keep up with the enemy as well.
hope this helps give an idea on how you'd like to build your vi