Help with RF Chieftan

I am following Pohx's RF Build guide, and am now L86. This is really only my second league. I aslo have a Warden and a Necro this league

However I stll find myself dying on various T16 Bosses or on some of the Unique maps, so want some suggestions for priorities for my next gear upgrade.

I currently have limited fund's (about 200 Chaos), so likely can only buy 1 or 2 pieces until I can farm some for currency.

Also any suggestions on the best mechanic to farm would be great as well.

I easily handle Abyss and Legion, am ok at Sim, and while I can handle the mobs on Breach, I seem to get nothing useful dropping. I don't have the currency to juice up Strong boxes, and I do get overwelmed at times on Expedition.

I have no idea how to progess Betrayal at this stage, and I suck on Blight.

My Character is available on Maxroll at
https://maxroll.gg/poe/planner/p07xq0qp

I also have a PoB but its not linked to Maxroll yet.

Any suggestions much appreciated.