My default summoner spell setup is flash & ignite, but if you're playing against a team with heavy CC you can take cleanse instead of ignite. You can also take exhaust instead of ignite if you're more comfortable with it.

For my starting items, I usually take Corrupting Potion for extra sustain in lane. But if you want to poke your opponent, push waves faster and do "cheater recall", you can take Longsword and Refillable Potion. Usually, my first back is when I have 1400 gold, or after my first kill. I look to buy Serrated Dirk and Boots. If you get a kill before collecting 1400 gold, buy Serrated Dirk only. For the first item I basically always buy Duskblade, but you can buy Youmuu's instead if you're more comfortable on it. As for boots, buy Mercury's Treads against a team with heavy CC, Ninja Tabi against a team with auto-attack reliant comp (I usually buy Ninja Tabi when behind). Mobility Boots are always a good choice, especially when ahead. I usually buy Edge od the Night for my second item, but you can buy Youmuu's second if you want. I choose my third item depending on the situation in-game. If I'm ahead I buy Guardian Angel, if we're behind I buy Youmuu's. The reason why I buy GA is preventing enemies to get gold from my shutdown, or at least making it harder for them. For my fourth item I buy Black Cleaver. Buy Black Cleaver only if against tanky team comp (Ornn toplane, Nautilus supp), or if you want to increase your own tankiness. I usually go lifesteal for the last item, as it provides easy health regen in the field.
Here are some good options for you to buy. Maw is really good when laning against a champion with a lot of AP. Sanguine is good if you want to search for solo picks in the jungle. Umbral Glaive is good if you wanna help to control the vision of your opponents. Sterak's is good if you want to further increase your tankiness. Items built from Last Whisper are good if you're trying to go for those one-shots.

In lane against champions that are ranged or have powerful single-target abilities, you should be holding Wild Enchantment (grass) most of the time. Don't forget to fully abuse your passive by refreshing Enchantments non-stop. When your jungler signals a gank, u should grab Ice Enchantment. If your jungler doesn't have CC don't refresh your passive and stun enemy champion with two Ice Enchanted Qs. Don't underestimate the power of Rock Enchantment, as it can be a safe way to last hit cannon minions and enemy champions.

Try to make a play when lvl 3, as you can easily kill someone then. Your basic combo should be:
E --> Q (Ice Enchantment) --> Ignite --> AA --> W (Rock) --> AA --> Q (Rock Enchantment)
If you use this combo when enemy is on 75% HP and before Lvl 6, you should kill him.
Later in the game you can add you R in this combo too. The best place for it, in my opinion, is after Q with Ice Enchantment, Ignite, or first AA.
You can later include your ultimate in the combo before ignite.

Your R can have many different usages depending on your team comp. With Taliyah you can connect different walls and make your ultimate larger. With Jarvan you can use your R inside his R, to have a guaranteed stun. You can also use your ultimate on the outer side of his R if he jumps into the enemy team. Never forget interactions that your R makes because they can sometimes save you or get you a kill. For example, you are low HP in the river and an enemy that will certainly kill you is right behind you. If you use your R and stun him with it, you can escape easily. And I'm not talking the stun you get from hitting a wall with it, no, I'm talking about the stun that you can make by using your R in the water or bushes. Even on the ground, you get a knockback, which can save you from enemies or get your Yasuo an opportunity to use his R. Meanwhile, you can get some easy finishes if you use your ult on the mid-lane wall next to the tier 1 turret, as you opponent may go to recall there, after you got him on low HP.