best chain lube tested: gasoline+manual gearbox oil 75W90 or something like this (2parts gasoline, 1 part oil), take the chain off, clean it in diesel fuel (let it soak a while in a container), let it dry or clean it with a rag, put the chain into the gasoline-oil mix an let it soak a bit, take it out an let it dry, the gasoline evaporates and the oil remains. clean the excess with a rag on the outside plates.
It's practically free of cost, gasoline/diesel/oil for gearbox is laying around in my shed, so no cost. just a tool chain is needed and also a nice chain that can be broken off easily (without hollow pins or replacement pins, maybe a reusable masterlink is best)