I could tell you how to do it.
The only thing stopping you is how many resources you have, so the solution to be found is to the question “How do I get those resources?” How do we get those resources? By any means necessary. What means are available? Quests/Story/Diplomacy Milestones/Research/Scavenging/Raiding. Are any resource gathering modes finite, or throttled in some way? Yes, every single one except Raiding.
Solution then? Raid. (I suggest Anu Food/materials, for ease, since there will be a lot of it)
WEEK 1
Step 1: The first week of the game your only goal is to build a Scarab, and you’ll complete that before the end of the first week.
Step 2: Find a nearby haven to raid, send your team with a scarab there, enter into the raid mission.
Step 3: Spend maybe 2 or 3 turns driving your soldiers to the nearby crates before evacuating the map. You earned maybe 300-500 materials/food, 5 SP on 3 soldiers, and about 3 SP into the general pool
Step 4: Repeat step 3 as much as you need to until you have 6-10 labs/fabs, 6 phoenix bases, and a few thousand materials/food and some tech.
WEEK 2
Step 5: While in week 2(or 3 or 4 if you’re just being lazy about this like I often am) and waiting for the fabs/labs to complete, just focus on researching main missions and doing them while building a second Manticore. Also transform a second base into a “training base” with about 7 training facilities in it.
WEEK 3
Step 6: All labs/fabs are done by week 3. You’re now building Aircraft at one a day, and vehicles at one every few hours. Fly around the world recruiting soldiers from every available haven (+ ones available in Personnel) until you figure you have enough. I didn’t rush this part as it didn’t seem all that important after acquiring a dozen soldiers, but I ended up settling with 45 soldiers by week 8 (end of the game).
WEEK 4 (and a bit of 3)
Step 7: Manticore/Scarab are being completed rapidly, and soldiers are quickly reaching level 7 in the training base. Begin distributing their SP and considering what roles you want each one to be. Consider the equipment they should equip, and manufacture it. Place them on the aircraft and fly them to their region to hold.
Once you get your 2nd team out, you can use the 2nd team to begin raiding for more resources while the first team focuses more on the story. While the 3rd/4th/5th/etc teams come out, they too just go do the raiding or gathering from LotA sites. So by week 5 (February) you should effectively have infinite LotA and regular resources. (Only thing making it not actually infinite, is that your RL time must be spent gathering these resources from these simple raids with little-no combat) The game, even on Legend, is easy at every step of the way because you’re always ahead of the curve. Recently they reduced the SP gained, and greatly increased the rate of Pandoran evolution to more closely match this level of progression.
Note: Stamina will drain from soldiers doing the raiding. It’s possible to still gain resources (especially if you have Ready for Action on any one of the soldiers) even once you reach 0 stamina. Edit: Personally I self-limited. I only raided a haven once every few days, and never twice in a row. I didn’t exploit the raiding by doing so with 0 stamina, nor did I exploit instant-evacs for quick SP. Even with these restrictions, everything occured in roughly the same timeline I gave you because the main issue was the build times on facilities and I settled with 6 labs/fabs at first, only changing to 8 of each by early february (probably better to do just get 7 fabs and at least 10 labs I’m thinking)
If you raid in this game, the cost of everything effectively becomes zero simply because raids pose no threat and are considered a free and infinite source of resources. Personally, I like the week1-8 gameplay I got going for the most part other than how resource gathering works. I’d like to be able to gain as many (or at least close to) resources by doing other things, I’d like raids to not be as exploitable, and maybe less total mission count in the game overall (considering more than half end up being raids).