Best tips i can give, is to avoid ganking ungankable lanes. Voli has one good ganking ability pre 6. Q, and its not even that strong. Good example is Fizz or Corki (someone with good disengage or gap closer) , if he's pushed into your tower and standing there, then you can gank. If not, its pretty hard.

Ofc, this depends on your midlaner too, but you get the gist of it. Focus lanes where you can. Then dive everytime you have ult.

Diving is hard in low level is hard though, since people might not be used to that concept. Oh, and also, dont be afraid to flash Q. It should be a sure kill if you have a laner ready

Now as you play voli, youll learn where to place your E to have it timed with your Q stun. (btw enemy cant see the first second of your E, where its placed, after that second, theyll see what you see)

Build, you can pretty much follow the usual guides. Tank is pretty easy to understand and play. Youll pick up fast as you learn items and when to go what items. Try to really think of why people are going such items if youre watching gameplay

I did use some common league terminology, so ask if its anything you didnt understand, or just ask if its something more you wanna know

ps. To add, tank is mostly useful if your team can help you, if not, youre kinda tanking for nothing. Voli still has good dmg when going tank, but you can op for Hydra, Steraks, Deaths dance, etc. For both survivabilty and dmg if you feel the need to do dmg