Value is a subjective question and as such, you can not make something worth anything else.
As such, your best choice is to create a cryptocurrency and make sure that all participants agree that it is worth the desired asset.
All other projects with oracles, "smart contracts" and so on are just a version of the previous social contract mentioned above between network participants.
If you still want to try to develop something, I advise you to take a look at MakerDAO and DAI from Ethereum, here. They are working on creating a stablecoin without any stable assets. Know that all people (myself included) have doubts about it.