Ryobi cs214 chainsaw what chain is needed for it?

Depends what it is you are oiling.

around 6mm
your local hardware will have special chainsaw files on the shelf

https://www.youtube.com/results?search_query=Ryobi+18%22+Chain+Saw+primer+replacement

Ryobi 18 Chain Saw primer replacement YouTube

Contact Ryobi via their website and they will send you the PDF - http://ryobi.com.au/

Just fill the tank with regular bar/chain oil available at home centers, hardware stores, and saw dealers. Don't use old used motor oil or similar. Hope this helps!

The standard chain file should fit it. It is about 3/16 dia. I found the dremel to work 10 times better, they have a little stone bit just for chains. Eventually, you have to take it in for sharpening, it will set all the teeth the same.

The drive sprocket is not expensive, but finding one is hard, The part runs about twelve dollars but its made in china and there are not very many dealers. TRy to contact them on line, Thats probably your best bet

If it is an electric chainsaw (not gas powered) then the only oil you need is chainsaw bar oil, which lubricates the chain and bar during use (self feeding system). This goes into the chamber at the top of the saw. You can buy chain/bar oil for chainsaws at any good hardware store or outdoor power equipment store. You can use any brand of chain bar oil, most are pretty good.

If it is a gas/petrol operated model, I will need to know the model number to advise on that.

loosen the two nuts that hold the chain cover on. Once they are just loose, then use a flat blade screw driver to turn the slot that you see right next to the base of the chain. Once the chain is tight, retighten the two nuts.

pull the barcover and bar off and you will see the clutch put the chain back on the clutch and put the bar back on and run the chain down the bar and put the cover back on and you will see a little screw in the bar cover are in front of saw by bar tighten that screw until slack is out of chain then tighten bar nuts.