>>1788712you could get one of these to check if it needs a new chain
lube the chain with some chain oil
get a bucket of hot soapy water and a rag and clean it, clean the brake track especially
then clean the brake track again with a clean rag dipped in isopropyl alcohol
surface rust on bolts doesn't really matter. The more important thing would be to remove them, clean then, and re-grease the threads. You can take the rust mostly off the heads with steel wool/wd40.
Also remove the seatpost and stem and clean/grease those.
If you want to do something somewhat difficult then overhaul the bearings. Headset, hubs, bottom bracket. Unless they're all totally smooth/tight.
oil the chain though yeah that's the big one. Get 'dry' chain lube as it's less messy.
