It is possible to fight without these resources. It isn't easy but it is possible. The late game you are going to want to secure these resources for yourself, and you will possibly have to trade with the AI for some of these resources in the mid-game. You are going to have to design troops that use a minimal amount of these resources and you can definitely compete.

Most of my starting positions do not have these resources, but I do acquire quite a few when settling my other 2-3 cities. Now if you don't have any of these resources even after you have settled 2-3 cities (or don't see any), then you may have a problem late game.

Mage Champs.

Actually my last game there it was really difficult to find and hold onto an iron resource, though I eventually managed to find some outlying and set up outposts to mine it.  Ended up building the Iron Works which further improved my advantage.  Although the AI did have iron they kept scrapping over it so they didn't have a reliable supply.  It was so bad they ended with metal resource in negative numbers most of the time (don't ask me how that's supposed to work...)

It's a post apocalyptic world, and yet you expect to find every and all resources right in your back yard?  It should be scarce, it should have wars fought over who controls it.

As you are seeing, random resources make that I usually choose between 4 types of unit-design:

- No resource- Cheap units. The best unit u can design without using crystal/metal. This is the body of my army.

- Elite. The best unit that uses big amounts of both. I usually wait untill fortress are developed, and I have enough resources.

- A bit of metal. Like sword+shield (around 7 metal), leather the rest. To improve the cheap troops, but without too much cost.

- A bit of crystal. This one is more rare, as usual crystal is more scarce, and slow to collect. But it  might happen. In your situation, you might train mages (with staves) for long range, that only require crystal, and cheap units to tank and defend your mages.

You can trade metal with AI, you can pay in influence, wargs or other resource you dont need.

Finally, prepare a cheap army, and meanwhile search where is that only iron mine, then plan an attack to get it.

 This is the good of the game: to force yourself to adapt to a new situation. It is like design a Sov with full Fire Magic, and then you can't find fire shards....

I'm basically running this in my LP vids.  No iron, no crystal, only a few shards and one horse stable.

Horses+spears = good enough hopefully.