How could we upgrade our gears into vinethron in the lost grove?

Cinethorn comes from battling I believe, I think it's the bosses. Stoneware is made via the smithing part of he barracks in the grove.

You can't upgrade one type of equip into another, just upgrade them into stronger versions of the same type

So an Exotic-level equip becomes and Exotic +1, Exotic +2, Exotic +3 etc.

Vinethorns are dropped by bosses of the lost grove (not elites, only bosses. You are guaranteed to get one from each boss fight though)

Stoneweave are troublesome- you need to get the Tomes of Knowledge that the cave bosses drop (legendary-rarity drop) to be able to unlock the ability to make any given kind (eg. stoneweave lightbringer bracer is one kind, stoneweave pyromancer armor is another kind, for a total of 18 kinds)
And that's just Unlocking them, never mind making or upgrading them (upgrading them to +1, +2, whatever takes Enigmatic gems, another legendary rarity boss drop)