There is no money in smelting for the sake of it, since ore and bars come out to the same value at the counter. Melt down what a recipe is asking for and leave the rest in ore form, which keeps your options open if you change your mind about the build.

the crimson half of the pair

This is the Crimson answer to Demonite, and the equipment made from each lines up tier for tier, so advice written for a Corruption world translates without much thought. What does not translate is the recipes themselves. The two metals are not interchangeable, which catches people who haul gear and materials between worlds and expect the crafting menu to accept either.