Chainrings and casette wears down because of the chain. Replace chain, SRAM with EzLink. Then take your chain off every 100 miles or so and wash it well.
It's clean when you feel no sand or dirt inside the chain, when you take it in both your hands and bend it side to side slightly. When dirt you'd feel like there is dirt inside the chain. Clean until it feels like brand new chain. Then lube.
Cross chaining, bad chainline, cheap chainring are also factors.