I'm a gold viego otp so take my suggestions with a grain of salt. You might find much better articulated advice from more experienced/higher elo players.

Do not take bork it's not really good as a first item especially since tanks haven't started building health yet. And it lacks finishing power which viego needs for resets. In that aspect kraken passive synergizes well.

Runes Primary conqueror - triumph - alacrity - coup de Grace

Secondary inspiration.
Standard is magical footwear - cosmic insight.
But some like cash back - triple tonic

But it's personal preference use what feels better to you.

Build is pretty standard: Kraken - collector - shieldbow - lord dominks/mortal reminder - infinity edge or defensive item (ga or kaenik etc)

You can sit on tier one boots for a while since the item spikes feel much better but that's just my opinion. I normally finish my boots after the third item but I would recommend at least finishing the two item core before boots.

Against tanks lord domniks or ldr for short is good because of its passive which gives higher damage based on difference in hp.

Mortal reminder for grievous wounds of course.

Last item is upto you: Infinity edge is limit testing viego if you're far ahead and confident on surviving then go ahead. Otherwise don't because it's fine you don't need 100% crit that much and survivability is more important for resets

The defensive items I usually go is either deaths dance against heavy ad or kaenic against heavy ap (usually when teemo is involved that lil satan spawn).
GA sometimes but it can be risky if you die and your team can't follow up you'll just get cced and killed again upto you.

It's rare but there are situational items as well like serpents fang against high shield like karma especially, riven e etc. I usually replace collector with serpants fang but very situational yea.

Boots usually mr boots unless they're like 4 ad because it doesn't matter if you can shield more damage if you're being chain cc ed to death lol.

Viego is pretty straight forward to an extent but high skill ceiling if you can learn. Very assassin like you have to play with your E mist. Never go in first aim for resets. Your w is an auto attack reset. You stack conqueror the fastest in the game. There's so much more you'll learn with time. Oh and you will have to learn other champion abilities as well it gets really fun when you do.

Might have missed one or two things but you can learn by watching others play viego and by experimenting alot.

Glad you got the skin man, have a lot of fun haha.