So, if you are still trying to get Lydia, I couldn't recommend more highly rotating gear to finish out the factions. The amount of time it takes to farm sets for 5 champs in every faction that can 3 star 19-21 is astronomical.
Instead, you farm silver each day and then use that to swap around your absolute best gear, and in particular, those regen and stun sets that carried us all through the 21s to get Lydia. And basically during these swaps and the final push, you steal gear from EVERYWHERE.... Clan Boss, Arena, other factions as necessary, taking screenshots and notes and replacing once you beat the 19-21 and three starred it.
Once you three star a faction, you put it on farm for a bit on a little lower level for the 2-4 weeks you are finishing out the FW grind. Spare gear and sometimes partially geared champs for just a bit.
After you have Lydia, you start focusing on equipping your teams to perma farm, because now you can farm any stage and get one star and it doesn't matter. You still get the glyphs and forge materials from FW20 regardless of stars. Early some factions will be less reliable and that's just the way of it.
But as you slowly farm more gear, you will get upgrades here and there until you have every faction on farm for both 20 and 21. It takes a bit, but not as long as you think, and naturally happens as you look for upgrades for your Arena and Hydra and CB teams.
Personally, after Lydia, while I was setting up my perma teams, I worked under the principle that the weaker factions got the better gear so that I could farm the higest levels possible on each faction each day, knowing that it was okay if Sacred Order 20 took 8 minutes so that Lizards could farm 20 instead of 16 max.