Assuming you want to solo and not just join a squad to get the higher tier component drops, Heres my suggestion :
1) get atleast the highest sigma variants of all the components (shield , plating , engine) you can afford to make your railjack not feel weak. Pick the hitscan weapons (talyn/ photor , i forget) for gunners as the AI sucks with weapons that have lead time.
2) Do not go directly to the high level , but slowly clear the proximas, saturn is very much manageable with sigma parts , collect resources and salvage over time and build the weapons you can afford (i personally prefer carcinnox on pilot but you may enjoy something else).
3) get enough intrinsics to have 2 crew as it will make the missions a lot more manageable.
4) put one crew on ENGINEER and one on GUNNER. the engineer is important cause the defender does not normally repair the ships , and your ship will most likely be destroyed by fires and hull breaches by external forces more than any boarding parties. Try to get engineer with as much repair skill as possible - repair skill is what will help keep your ship healthy (few points of repair on gunner too).
5) The gunner should take out most ships so you take less damage anyway and keep the heat off you so you can focus on the objectives.
6) Tactical mods like void cloak is very useful in early stages to keep the damage to ship at minimum.
Efficiency is the dump stat for Mirage as her most commonly used abilities on a typical build (her 1 and 3 ) are very cheap.
Her 4 is too much of an energy hog and provides very little damage and utility in return.
So near 200 duration and 200 strength is suggested.
Umbral vitality and intensify ,
Primed continuity , consituituon , augur message should push you into that duration.
And a single fully (or partially) modded blind rage should now put you at 250 strength.
That leaves 2 mods , the hall or mirrors is a good augment and you could add streamline or primed flow to manage the energy a little better.
That is of course the typical weapon specialist build.
There is also the explosive ledgermain build.
Where you focus on range (230+ to cover most rooms), some duration (150+) and decent strength (180+) along with the explosive ledgermain augment.