On level 1 Qiyana you either want to start w or q depending on the matchup. Normally you start q against a ranged champed or someone who can poke you down (IE. Talon). If they are a melee champ, starting w is viable to try and provoke an early fight using your w as a gap close and an auto reset

When you hit level 2 using a long range w and q can be useful to pull off a safe trade. If they ever try and hard engage you using q into w into q would be your best option. I advise that you play safe and wait for you level 3 spike

From levels 3-5 In MOST matchups, Qiyana becomes a very strong opponent that the enemy should respect. If you are playing against somebody who cannot fight back very well (IE. Kassadin pre six) then you should be trading them constantly when they try to walk up

if they enemy is at about 65 percent health after you hit six then I would consider within kill potential especially if you still have ignite. Once you hit 6 and gain your R your team fighting becomes amazing if you can set up a good ultimate. Try to get solo kills and roam the map to help your teammates become strong aswell!

W - Q ( like I said in lanning phase you use this "combo" for a long range trade pre-3 or even after)