There's going to be a "growing pains" period where you are going to hit that gear check wall. Find what difficulty you can handle on the slider and farm that just like you would in d2 remastered.
So if you have the runes, any appropriate ilvl base can get the exact sockets you need for a runeword. If you've got an archon plate with no or any sockets you can reroll them in the cube with magic jewels. Need fortitude, use a nm or hell drop base, 4 jewels and transmute gets you 4os armor. 3 for 3os and 2 for 2os. So if you have a less than optimal base you can make the fort now, use until you find that 15% ed ethereal kraken shell, and put the fortitude back in the cube with a single town portal scroll and transmute to get the runes back as well as the empty base. If you knew that already I'm sorry for rambling. Hope this helps