Life Orb is a good item, but it negate Multiscale. Btw, your Dragonite isn't faster. Lefties let it survive more. Since it has Protect like other VGC Pokemon. Yache berry is good, too. Because Dragonite is 4x weak to Icy wind. That slow down Dragonite. That's why Yache berry is necessary, but lefties and life orb isn't bad.
Icy Wind, Rock Slide, Discharge, Dazzling Gleam and some other moves are very common in VGC. You need to hit hard before they can use Rock Slide or Icy wind. Focus blast would not be bad.
In my opinion, give it Yache berry. Although Lefties and Life Orb is good, too.