Yasuo's champion.gg page
To answer the questions you directly ask:
Attack Speed or AD Reds and Quints/Magic Resist Blues/Armor Yellows
Statikk Shiv, Berserker's Greaves, Infinity Edge, and Bloodthirster are your core (don't necessarily build them in that order. I personally like and tend to get away with Tier 1 boots and a Vamp Scept before completing IE). The rest should be tech items specific to the enemy team and how to counter them.
As for general tips:
- Level your E first. Maxing Q does virtually nothing compared to a more fluid dash and Magic Damage to mix over your AD. You should start leveling Q once you feel that E is fluid (typically rank 3) and you have completed your Statikk Shiv.
- Yasuo's actually stat checked pretty bad in many trades. The super secret
Yasuo Melee Mid Laner trick is to engage on the enemy immediately after they burn an ability, say after using it to farm, if they miss, or if you block it with Wind Wall.
- Learn how to control Minion Waves. You are Yasuo, you have enough AD to freeze the lane without ever missing a minion and you have enough wave clear with your Q and Statikk Shiv to shove the lane whenever you want. If you can abuse wave control and force the enemy mid laner to overextend into your freeze, or if you know you'll win the attrition game without putting yourself at risk and shove the lane to pressure the enemy laner, then you can easily turn a winning lane into a dominated lane, or much more easily recover from past mistakes.
- Early Magic Resist or Armor are not terrible investments. I said those first 4 items may be core, but sometimes you gotta recognize if you're playing against a natural lane bully and build properly to deal with them.
- If you're playing Draft mode, try to pick Yasuo after your Top Laner or Jungler picks a Magic Damage heavy champion, or ask them if they could do so if they're picking after you. Don't be selfish and unbalance the team by making all the damage on your team Physical.
- Unless you know how to create a pseudo-1v1 in a team fight, which I assume you don't given the want for advice with Yasuo, be really careful about team fights with Yasuo unless you know a good ult will either set up the rest of the team, or get one of the enemy carries dead. You are a hybrid DPS/Burst Carry, you are not a Tank or Bruiser. Staying alive to pump out damage over time is infinitely more useful to your team in a team fight than it is to throw yourself into the enemy team and eat all their shit.