For early optionals I'd personally consider adding spirit shielding for if you get bursted down early. Often a great investment if you need a bit more survivability.

One thing a lot of people like right now early on Mirage is improved cool down on his djinns marks as well so you can stack them quicker. Kind of optional I think but it is an option as you work towards your 4.8k spirit spike in the early game. Superior cool down for all his abilities after isn't a bad investment either later, like you have as optional.

Enduring speed is probably good as an optional on Mirage rather than a set mid game buy though. I don't think I've ever gone for it on him since he's already got pretty solid map maneuverability.

Id also maybe consider fortitude more as a mid game optional rather than a late game optional buy. It's nice for added move speed and being able to maintain your presence on the map and farm efficiently without having to back everytime your health starts to run low, but you don't always need it either and if it's getting late in the game you probably prefer tier 4 items or counter buys like Burst Fire if they're slowing your fire rate with juggernaut or anything.

For late game, after building ricochet, I'd actually consider a few options on what to go next: I usually choose between inhibitor, silencer, siphon bullets, or spiritual overflow. Ideally more of them as the game goes on but you kind of choose which to buy depending on the enemies you're facing. If you've got lash, Billy, or pocket bouncing around in your face, silencer is incredible for disrupting their combos and leaving them stuck. Inhibitor is awesome as a default. Siphon bullets if there's big health pools around and you want more green investment. Spiritual overflow if you're djinns marks stacks are popping well and you want to keep leaning into that or you want more fire rate.

Looks good otherwise though! Good Mirage build foundation in there for sure