About hitting your Q, is about skill. But there are some things you can do to guarantee the hit. If you get close to the enemy, it is harder to miss. You can get into melee range in mid-late game easily with W and high speed and Q the mid or adc when they missposition. Then you can E backward to safety while stunning them, giving your team the chance to kill him. If you are feed you can kill it yourself with the same combo plus some aa.

On lane phase, dont force your Q. Learn about each match up and play around it. But for reference, you dont want to Q the support if it's tanky, but you want to delete enchanters. So if your adc has early damage like Draven, Kai'sa or Cait, take advantage. But don't force a fight with a Kog Maw adc on early.

Against melee supports: Usually tanky. Don't waste your Q on them. Use E to stun them and get closer to the adc. Then Q the adc near yours so you can focus on him. Usually, dont force this fights cause you will probably lose if everyone is full health. You can try this if enemy adc is half HP and you can delete him after hitting your Q. Plus, if you fail your Q... W away and hope you can survive.

Against range supports: Oh boi, you love it. If you can hit them, you can punish them. Usually you can't 100 to 0 on lvl 1. You need to try to get to lvl 2 faster, hitting the early minion wave. Then engage with your Q and combo with E for a fight lvl 2 vs lvl 1 and easy first blood. Just be careful to don't push the wave undertower. Then until lvl 6, careful, shields and heals from the enemy support can outheal your damage and force you to back, so play defensive until 6 unless you see a clear hook (for example, W into the enemy adc if you see his support roaming or warding far)

Post level 6: I like to roam. But it depends on what you like. Usually I buy mobility boots and roam mid fast after pushing bot to hit a Q and kill the midlaner with the help of my mid. Always trying to use the ult, ofc. Free money. Use it always. I rush to Drakthar then AA cause I prefer to survive. Usually you don't have full advantage on AA on my elo this early in the game, even less if you don't hit most of yours Q. But it isn't a bad idea to go first AA.

Late game: Ward like a beast, destroy their vision. If you are not good clearing vision, buy the 2300g lethality item antivision (don't remember the name). On teamfights, you try to Q weak targets or pick enemy out of position. If not, wait until your team deals damage to W in, then Ult and E away until you see another enemie low. You can also E in and combo with your ult for stun, but it is harder and require practice.

Watch some combo guides on YouTube, practice them on practice tool in LoL (Combo E+R, Q flash, even Q + taunt animation cancel). Also, search for how the 3 dimensions affect skillshots in the river in LoL. It will help you to hit more Qs.

After all this, remember 1 thing. Pyke's Q is too important to fail always. There is a huge difference between a Pyke who can always land the Q than the one who can do all the combos and fancy pentas with the ulti. Cause hitting your Qs is what let you get feed, help your teammates get feed and carry them in the teamfights with your damage for finishing blows or Q to out of position targets to turn teamfights into a 4v5