This build is mainly focussed on not-running-out of energy. I will explain here.

At level 1 I prefer Subtlety for more and faster energy reload.

At level 4 I always pick Relentless Striker. This is because when you 1v1 and they try to run, you can constantly dash towards them and you will most likely kill them.

My playstyle with Valeera is jumping in, deal damage and run out. Wait a few seconds and do it again. You won't lose much health if you do this properly. This is why I don't need Slice and Dice nor Mutilate since range on your Q is important for this combo. Only Fatal Finesse is left.

Level 10. I did build alot of reducing energy cost so smoke bomb isn't that satisfying anymore. However Cloak of Shadows gives you the opportunity to stalk/escape during a fight when properly used.

The level 13 depends on enemy team build. It's between Blind and Strangle. Just go Blind if they have a carrying attack speed hero. Otherwise go Strangle.

Now level 16 also depends on the enemy team. When you find your enemies wandering off alone alot, Go Assassinate and engage with your stealth Q for some heavy damage.

At level 20 I usually go for the extra movement speed for a faster positioning or escape. When the enemy team has heavy CC you can also go Enveloping Shadows.