A few drops of chain lube will keep your cranks spinning smoothly, as long you choose the right type
Apply It Right
Many lubes come in squirt bottles, which allow you to deliver a precise dose to each link of your chain. Less common (and sometimes less effective) are aerosol-based sprayons, which disperse the lube into every nook and cranny. Be careful not to accidentally coat your rims or rotors, which could impair braking.
Wax-based varieties go on wet, then dry into a dirt-repelling film. But the wax itself can build up on your chain and the lubes don't reduce friction as much as some others.
Many wet and dry lubes include the chemical PTFE (better known as Teflon), which can lower friction, so you might need less energy to turn your cranks.
Most lubes are derived from petroleum, but a handful use biodegradable vegetable oil instead. They're not as slippery, but are nontoxic and better for the environment.