Once you've hit endgame (reached MoF), there are several items you're going to want to acquire as soon as possible Here is a general strat, in order of how quickly you can start to farm them.
Siphon of Anguish is a very common drop off of Shade of Orobyss, which you will encounter often while pushing through a timeline web. Take him out early, and you'll likely find one on the first kill. You can also farm him for versions with legendary potential, but I suggest waiting until you've reached empowered timelines before worrying about making legendary items.
PrefixIncreased Warpath Area idols provide a lot of benefit and don't require a lot of effort to farm. Completing echoes with idol rewards is your best option, and it's worth deviating a little bit on a web in order to get these. If you happen to get Pride of Rebellion on your Abomination kill, that's a bonus.
Darkstride is a common world drop, meaning there is no specific boss to target. If you happen to get a Rune of Ascendance, this would be a good place to use it. Otherwise, you can farm it off of the Spirits of Fire timeline (preferably empowered).
Wings of Argentus and Throne of Ambition drop from the same boss: God Hunter Argentus in The Stolen Lance timeline. Wings only drops in empowered, and Throne benefits from corruption, so I highly recommend farming them together. You can either choose to farm these as soon as you hit empowered or pick up a few blessings first. Grand Patience of Herkir
and Grand Survival of Might are good choices if you decide to go the blessings route.
Apathy's Maw also drops off of Shade of Orobyss. It requires 50+ corruption in order to drop, which effectively means you'll need to wait until empowered timelines to farm this. As soon as you hit empowered, I recommend focusing on it while doing Wings and Throne runs.
Shattered Chains drops off of 120+ corruption versions of Shade of Orobyss. It isn't a particularly necessary part of the build, and doesn't gain nearly as much benefit before you have Grand Patience of Herkir. It should drop naturally as you're killing shades while farming blessings once you get over 120 corruption.
Monolith of Fate - Due to the nature of how timelines work, there are currently two highly desirable rewards from completing each echo. First, the echo reward itself, which is specific to each echo and clear to the player before they enter the echo. Second, stability, which is gained both from killing enemies in an echo and from completing the echo. It turns out that both of these rewards encourage completing echoes as fast as possible, especially on this particular build. Completing echoes quickly gives the player more echo rewards per hour. Additionally, since each echo rewards a baseline level of stability, the more echoes that are completed, the more of the stability reward is earned. Furthermore, echoes that are further from the center reward more stability and give better echo rewards, so pushing outwards as fast as possible grants access to the better rewards sooner. And if that weren't enough, we also want to push through the timelines as fast as possible to get to empowered and begin to farm our blessings and other rewards that are only available in empowered.
The one downside typically from going fast is that we lose out on bonus stability from ignoring enemies in our way. However, with this build, our echoes will clean up basically anything that is chasing us, mitigating this problem completely. It's also not really worth deviating from the objective since it actually slows down stability gained per hour due to getting fewer echo stability rewards (we also get fewer general echo rewards). All of this is to say that generally, the most efficient strategy for the Monolith is to run directly at an objective as fast as possible and complete it as quickly as possible, only maybe stopping to kill a rare here and there that might not die from our echoes alone. The one downside to this strategy is that some items will drop off screen (since the enemy died off screen) and if it's not a unique we won't know about it, but this is a more than acceptable loss since the echo rewards are a much better source of items than random enemy drops anyways, and we'll get more echo rewards with this strategy.
Arena - There are two strategies to dealing with enemies in the arena. The first is to orbit enemies, allowing our substantial area with Warpath to hit enemies while staying out of melee range. This also allows echoes to be created, which require the player to move a certain distance in order to work (moving back and forth generally will not generate echoes unless the movement is far enough). This will work for most enemies, but at higher waves some may be too dangerous and require the player to have substantial distance between them and the enemy in order to counter any projectiles or telegraphs. In this case, the player can just run directly away from the enemy (while avoiding projectiles and telegraphs) and allow the echoes to do all the work. Since enemies will always run directly towards the player, they will always end up running through the echoes, which will also maintain leech uptime for the player.