The tiers are coal/stone -> Copper -> Tin -> Bronze -> Zinc -> Brass -> Iron -> Steel -> Adelite -> Mithril -> Adamantine -> Titanium
(This info is accurate as of the current version at the time of this post, Version 0.0.9E)
You need to have a Hammer of TIER or higher (Higher just means it'll be a higher tier than whatever one is being mentioned) (example, Iron or higher to get iron requests)
To get TIER or lower requests
On REQUESTS only, non-specific you can upgrade ONE Tier
(Example: "I want a copper polearm and a round shield" -> Tin Polearm -> any shield (Could even be titanium, whatever your highest metal is, that you have 5 ingots of, should be what you make shields out of, AT LEAST IN VERSION 0.0.9E)
(Example: "I want a tin one hand sword, with an uncommon grip, an embossed blade, and an 1h guard v4" -> Must be Tin. Get a specificity bonus for having parts matching the request, but I don't think there's actually a trigger in place to prevent accepting the item if its not 100% exact, it just needs to be tin, I could be wrong, I don't botch enough orders to be sure)
To mine you need TIER or higher Pickaxe, no upgrades
To get requests you need TIER or higher Hammer, "No upgrades" on requests, specifically (They won't ask for Tin if you only have a copper hammer, but you can sell them tin for copper requests)
Sale can be upgraded by ONE TIER, or downgraded by unlimited TIERS, unless specified.