At the bottom of the guide is a complete calendar of events, listing every 111 days of the first playthrough. (I'm currently going through it again to see if everything I did the first time is applicable to others.)

Otherwise, you can check out the individual sections I've written out.

The mission locations for Psi Gate & ADVENT Forge will spawn three tiles away from your HQ. (I believe, I haven't 100% confirmed this yet.) So don't contact a new region unless its completely necessary.

Building Proving Grounds & Shadow Chamber (I don't recommend building these two at the exact same time.)
March 28 - April 4

Building Skulljack (While you're building Skulljack, research the Blackvial in Shadow Chamber.)
April 4 - April 17

Codex Brain
April 20 - April 24

Codex Data (Do the ADVENT Forge Mission while this is being researched.)
April 26 - May 4

If you follow the above timeline in the same order, once you obtain the Psionic Gate, its a straight shot to the finish. Theres only two more research projects in the Shadow Chamber before you Assault the Network Tower/Alien Base. You can start skipping missions if you want to once you complete the Psi Gate mission.

Keeping your soldiers healthy is probably the most important part about this achievement. Since this is a rushed campaign your roster is going to be incredibly small.

Soldier classes aren't too important. I know there are some easy ways to get Psionic units with mods, but I didn't end up needing to use any.

My roster consisted of a Scout Ranger, two Support focused Specialists, a Sniper, and two Demo Grenadiers.

Don't let the idea behind this rushed campaign trick you into playing missions fast, you're going to want to play like a turtle, slowly and safely. In order to do that I used these class abilities for my soldiers...

Phantom, Shadowstep, Run&Gun, Implacable, Untouchable.
Your ranger is the frontline, use him to spot pods before they're activated. You want Ayys to trigger on their turn - which usually gives you two shots on them before they can react. Shadowstep is amazing, especially when paired with Run&Gun. Implacable and Untouchable are the go to for any ranger.

Combat Protocol, Haywire, Scan Protocol, Threat Assessment, Evervigilant, Guardian.
Combat Protocol gets you the secured kill on the Lancer who took 7/8 damage. Haywire is an extra unit if you're lucky, Scan Protocol is essential against Chryssalids and pods the Ranger hasn't scouted. Threat Assessment is the most important ability it gives your front line two attacks in a turn. Evervigilant allows you to use Threat Assessment, move and still overwatch. Evervigilant is great if your Ranger has blown his conceal and you want to trigger pods with a specialist - but Guardian is probably a safer ability. Specialists give you a lot of room to work with.

Just build all Sniper abilities and stick him/her in the back. (Probably my least favorite class.)

Shredder, Demolitionist, Heavy Ordnance.
I didn't get to level my Grenadiers up as much as I wanted, my original Grenadier was injured much more than he should've been, and my 6th unit was underleveled from missing so many missions. Still, Demolitions is great, if you can't take out the enemy, take out their cover and allow someone better to get them. Demolitions doesn't work against anything other than cars, so don't bother with it at the moment.

Sniper: Scope & Auto-Loader.
Support: Repeater & Stock.
Ranger: Laser Sight & Hair Trigger.
Grenadier: Expanded Magazine.

Sniper: Scope is obvious, but Auto-Loader is great for the turns after you use Killzone. The only justifications I can see for Auto-Loader being used on another class is for something like the Grenadiers spray ability.
Support: Give the supports the repeaters and stocks. Repeaters can trigger off of stocks' guaranteed damage. Hair Trigger is alright as well.
Rangers: Crit and another shot with the OP shotgun? Damn.
Grenadiers: I'm not too worried about the Grenadier having weapon mods, expanded magazine is cool, but I prefer all other upgrades on someone else.

Mission Selection is deceptively tricky, well sorta.

You want to prioritize Engineers=Scientists>Intel>Supplies
Everything else is expendable.
However, make sure your first scan is either an Engineer or a Scientist. It doesn't need to be, but you can easily get screwed with worthless scanning locations.

Picking Between Scientist and Engineer rumors

March-April: Scientist
April-June: Engineer (Unless your buildings are complete, as well as your two shadow chamber missions.)

You want scientist early because Engineers are only important for getting to the Advent Forge and Psi Gate(What I mean is Engineers need to fill upgraded Power Relays and Resistance Comms so you can reach the missions). I finished all the buildings I would need by late March, and hit a rut when I didn't have enough scientists to complete a Shadow Chamber Research.

Picking a Guerrilla Operation

Same rule applies as rumors, except try to counter Dark Events that make your life harder.
Dark Event Priority:
Hunt XCOM - Best to counter
Alien Cypher - Best to counter
Rapid Response - Good to counter
Informant - Good to counter
Viper Rounds - Good to counter
Infestation - Good to counter
Vigilance - Good to counter
Alloy Padding - Good to counter
Resistance Informant - eh
Rural Checkpoints - eh
Inflitrators - eh
Avatar Project: Minor - Best to ignore
Avatar Project: Major - Best to ignore
New Construction - Best to Ignore

You're going to be ignoring the Avatar Project as much as possible in this run. I didn't counter a single Breakthrough, or do a single Facility mission and was still able to get through.

Scans

This was my entire campaign's Geoscape activity (not including my visits to the Black Market). I didn't get very lucky with rumors, so I focused on using the Resistance HQ's rapid construction/healing.

Theres one important thing to say about this section. Never buy anything until you know its necessary. This means you're going to be piling on a lot of money. You might think you have enough to buy some luxuries, like an early Mimic Beacon or a GTS upgrade, but don't. Its crazy how fast your stockpile of $700 can go down to $2. (spoiler: its one day.)

Don't buy a single thing in the Black Market. You're going to need ~320 Intel depending on your Mission Spawn points. My two missions spawned three tiles away, for both the Forge and the Gate.



If that happens to you, just do what I did and pay,
40 intel >> 80 intel >> build radio tower >> 40 intel
Saving the 80 intel isn't worth the extra time and supplies of reaching the third tile.

Once you've obtained those two tiles you can either spend extra intel in the Black Market, or save it for bonus abilities on the Pre-Final mission. I got very lucky with my council missions giving me a lot of intel - it might not be the same for you so plan carefully.


This is the entire purchase log of my run through.

**

**Don't buy Smoke Grenades, apparently they're bugged as of March 16th.

As you can see with the dates, I stockpiled my supplies until I bought achievement critical upgrades like story required buildings, or upgrades.

Building Order is a lot less important than I originally thought it was going to be. If you get early Engineers and supplies, you can be done with excavation/building by very early April.

My build order:
GTS >> Resistance Comms >> Power Relay >> Proving Grounds & Shadow Chamber >> Power Relay to power Shadow Chamber upgrade.**



(** I didn't end up finishing that second Power Relay, instead I just destroyed my Proving Grounds to get the last bit of energy I needed.)

Tech is also straight forward.
Essentially all you want to do with tech is rush any essential to the story, as soon as you get them.
Those being:
Alien Biotech
Advent Officer Autopsy
Resistance Comms
Alien Encryption
Black Vial
Codex Brain
Codex Data
Psionic Gate
Avatar Autopsy

In between those, grab whatever luxuries you want to get, I recommend just focusing on Magnetic Weapons, and Plated Armor. Some autopsies can be done as well, but I didn't worry about them. A good one to grab that I didn't would be the Muton Autopsy for Plasma Grenades.

**March 21-24 I made an error in excel. I say that I start excavation 5-8, ignore that. It was supposed to be excavation #4 four times.**