Xayah should be focusing almost constantly on her CS early in lane, let your support do the poking for the most part. You can combine CS'ing with poke by using your Q and positioning yourself just right to get a little bit of damage on enemy laners. You would ideally not engage at all until level 2 so you have your root ready. I often find it easy to get kills at level 2, but I almost guarantee I get a kill by level 3 because of how strong her kit is. The range on Xayah's Q is almost twice that of Caitlyn's auto attack, so keep that in mind when you are poking and leaving feathers to root later on. You can play well behind your minions and support and still be able to root and follow up with heavy damage.

Engage with Q, immediately use your W and start pelting the enemy, root them as soon as you get 3 or 4 feathers behind them. A mistake most people make is trying to line up 5 or 6 feathers, when in reality most of those are not going to hit just because of the pathing you take during a fight. No intelligent enemy is going to be standing still letting you stack a pile of feathers behind them. You have to be playing fast, making sharp plays, and catching people off guard. When the enemy is under their tower you can just throw a Q and immediately recall it for easy damage.

Punish overextension whenever possible. I push my lane up the enemy tower and hold it there as long as possible. Xayah has insane outplay potential, so you can repel a gank with your support very easily. I find myself getting early doubles or triples from punishing junglers who underestimate this champion. Deny the enemy as much CS as possible and farm those plates early. You should ideally be getting first tower with all plates by 15 minutes every game.

You need to be building appropriately for the enemy team. Most of my games I am going Kraken slayer because Xayah works amazingly with attack speed. Understand that Xayah is one of the least played ADC's in the game, and the people that do play her have low winrates, under 48%. People expect you to do badly, they don't understand her kit, they will not realize what hit them if you build properly. Her kit is overtuned, but people build her completely wrong.

Galeforce is good but people build it almost every game on her. She does not need the active from Galeforce to be good, I barely ever see a chance to use it, mostly because I kill the enemy before needing it. People say that Essence Reaver is a MUST on Xayah, but I have never built it once. It's useless. You do not need that empowered auto attack or the mana refund. The faster you get your feathers out and proc Kraken Slayer, the sooner the enemy will die. Attack Speed, Crit, and positioning will carry your Xayah games. I see most people building Phantom Dancer on Xayah, but Runaan's Hurricane is just so much better. You can be dealing insane amounts of damage with very little effort and winning most of your games even if you have a braindead team.

I laid out the reasoning for each build path in the item section, they are pretty self explanatory anyway. You want to get 100% crit chance every game though, and no matter what Infinity Edge should always be your 3rd item.

You are a do-it-all champion. You can nuke a squishy, shred a tank, outplay the most mechanical champs in the game, solo Baron and Dragons, and wave clear 3 open inhibs while your team ends at the enemy nexus. No matter how badly you do in lane, once you are full build you have zero excuse for not carrying in team fights as long as your team is actually trying to win. The only way you lose as as fed Xayah is if you mess up. Your skill is the limiting factor in this champ.

You should be leading the fight with Q, and using W on tanks more than anyone else. Save your R for once your team has engaged and the fight has already began. It will have the most impact mid-fight, and in solo queue it will really help your team see how easy it is to finish the fight. Runaan's will make teamfights go so fast it isn't even funny. Just throw your Q, W away until you have max feathers and pull them back. If you have Navori Quickblades you will be rooting people every 3-4 seconds, entire teams almost. If you have a good frontline, the match will almost certainly be a cake walk. Use your R+Flash combo to take enemies by surprise while retreating or kiting. Xayah is a burst damage god, just use the element of surprise and you can clean people up.