Coming of my extreme goodness in the More dream types suggestion, I has moar ideas
RUBBER That’s right, bold underlined and italsized!
Anyway. Rubber would be found in pools in caves. It would also be found randomly by breaking a wall while mining,(No you wont die)
Rubber would be used for building better carts, making walls more resistant to attack("Damm, my battering ram keeps bouncing off!")
Better oxcarts, and you could make a bouncy ball that you throw at your enemys

Rubber first comes in crude form. You cant do anything with crude rubber until you refine it, so it sits occuping space in your large chests like a useless pile of crap. You can refine it by boiling it in a cauldron. Once you refine it it looks like a black disk untill you make something with it.
OIL
I am pretty sure this has been suggested before but whatever.
Oil would be found in the ground like rubber, but you get it by making a wall. Once you make a well it has a 10% chance of turning into a oil well, and you only get oil from it then. Once you get oil, you can use it to power stoves(More on that later) Use it to power basic machines(More on that in a later post) and use it to make bonfires, which are like normal fires only bigger and a shitload brighter. Once you get rubber that’s it. Make whatever you want with it. Viola
Anyways, thanks for reading, bye