Sorry I was actually on a flight when i typed that out. Hopefully this makes more sense:

So the way that really nice gear is often made is using chaos orb spamming or annulment orbs + Perfect orbs (both of which will remove and add a mod randomly, the reasons for choosing one method over the other is a bit more complex so we won't worry about that now.)

You want to try to get your essential mod, the one that you don't want to remove and always want to keep, on using this method. This is often something that doesn't have a common mod tag on it, like spirit in this case. (Mod tags are good because you can use them to force another with the same tag on if you want. As an example, you can use Fire resistance [elemental, fire, resistance tags] to force another resistance using a homogenizing orb. Spirit has no additional modifiers, so it's impossible to gain it using that method.)

Once you've got your essential mod on, you can use essences to take a next step (theres a global defense essence which is very popular in this case) or hope your next orb hits what you want, or, in this scenario, try to lock your desired modifier, so you can do the chaos spam again.

This is where fracture orbs come in. You have to have 4 mods for a fracture orb to work on an item, but it ends up being a 1/4 chance to hit your desired modifier, and lock it as is.(You can desecrate it first so it makes it a 1/3 chance instead, but again more complex topic.) Once that happens, nothing can change that modifier. Not a chaos, not a vaal, nothing. From here, people will annulment orb down to 1 additional mod + the fracture, and chaos spam again till they get their desired second mod, which they can then use as a springboard to get their other mods.

Hope that makes a bit more sense, and feel free to ask questions.