That old of a bike, new sprocket bolts are cheap. Get them with new nuts.
Chain, renthal r1 chain or the EK MRD chains work great. I dont like O, X, T or anything ring chains. dirt gets in the rings and causes binding on the chain very quickly. at that point, you need to throw out the chain or spend to much time cleaning it. Standard chains work best.
Sprockets if you are just woods riding, buy steel. Either inexpensive like JT steels front and rear or what ever you can find. Should be about $12-25 front-rear prices for steel.
Tires, great trail riding tire is the maxxis 6001 series. It runs a bit narrow, so go the next size wider. They last for ever and hook up great!