Money solves the problem of double coincidence of wants. In your barter economy, how does the dairy farmer get new clothes if the tailor is lactose intolerant? He would have to trade his milk to someone for something that the tailor would want. This becomes inefficient. Money allows a medium of exchange that can act as a universal means all parties would accept.
And the process you describe continues until the best form arises that satisfies the qualities that best exemplify money. Qualities such as divisibility without destruction of use value, does not spoil, not easily counterfeited, etc. Historically, precious metals have "fit the bill" as they perform with these considerations in mind as the best form of money.
Interest is not an evil, it is the price of time. If I were to offer you $10,000 today or $10,000 in ten years, which would you choose? Obviously, in order for you to even consider the later option, I would have to raise the amount in the future. Interest is just the price you pay someone to not consume their money now. There is nothing inherently "evil" about interest. Elites can pervert this tool as they do with so much else, but it does not mean the concept of interest should be discarded.
I agree the current system is not to benefit us, but the concept of interest is not an invention of evil. It can be perverted and used for evil like any technology can. Your cell phone can be used to send voice-2-skull transmissions but that does not mean that is the sole use. Interest does benefit me in as it provides an incentive mechanism for someone with excess resource to lend to me. This process gives me access to funds (to grow buy machines, pay employees, grow business, etc) that I would otherwise not have. Just because some abuse lending (both lenders weaponizing this system, and borrowers being shortsighted and irresponsible) does not mean it is without merit.
I think I may now understand the source of our disagreement. I am speaking of interest as a general concept as in me loaning you money. You are speaking of interest as it relates specifically to central banking. I am in agreement with you that The Fed interest is indeed an example of weaponized interest and fight along side you in its demise.