can i use a 9 speed chain and cluster in a 10 speed shimano set up need to save some cash
No, otherwise it will start skipping chains.
Tried this before. Installed a 10-spd cogset using a 9-spd chain. Wondered why, despite my continuous tuning, my chain always skipped. Went to my LBS and changed my chains to 10-spd specific, problem solved. Try comparing 9-spd and 10-spd chains, you will see the 9spd chains are a bit thicker than the 10spd.