Here is my guide to farming gear.
Go get all the supporting pieces you need!
You can also upgrade current gear at the mystic. You are already using icyviens. There is a Gear Page that will list the priority for stat on every item in the build specifically for the build you are looking at. Following that is a great way to start.
If you have 2 of the same item, you can take the lesser of the 2, and reforge the legendary item in the cube with recipe 2 (I forget the name). This is expensive on mats, but it is the best way to target specific stats on a specific pieces. Like being ancient, for example.
The only way to get more L-gem is to do GR. One will drop every GR until you have them all. If you sell or leave them on the ground, the game thinks you don’t have it, so will give it to you again. So keep one of each in your stash.
Adding lvl to the BotP which is common to get really early/first is not going to be a waste. When you get the others you need, you can start on them. Getting your main gems to lvl 25 s/b a priority.
These recipes only drop from bounty cache. Yes, you do want flawless Royal everything if you can. Split bounties are the most efficient. If you don’t already know, this is entering a random bounties game, each person does an act of bounties on tier own. Everyone does the last act. Everyone gets all 5 cache for doing about 28% of the work. Might be hard to find a full group at T6 at this point in the game, but you can probably get lucky on a weekend.
There’s lots, but you can only focus on so much at a time. These things, when finished, can catapult you to GR90.