If you're wondering how you access marble and plank boosts, you only get one boosted manufacture for each "level" of goods.
So out of Steel, Marble, and Planks, only One will be affected by relics collected.
Same for Crystal, Scrolls and Silk, etc etc.
Now it's best to solve all possible encounters, cause cleared zones open up more zones - plus zone clears will provide expansions for your city. But if you have boosted steel, you won't have boosted marble/planks no matter how many marble/plank relics you gain.