94' Pontiac grandam GT(manual transmission)

Hi, the other day while I was waiting at a redlight my car died. Now I didnt even realize it had died cuz the music was going, my husband and I were talking etc. So I had figured I stalled it and tried to restart. Well it wouldnt do anything. It didnt try to turn over or anything. The battery light came on and another check engine light. We called a mechanic and it was suggested to us that it was the starter. So we replaced the starter and we ended up killing the battery trying to get it started. We decided to try a new battery. Nothing works. The car worked fine before that. Starts up everytime and now all of a sudden out of the blue it just dies while running. The mechanic thinks it might be the alternator now. The car wont jump start and just makes a loud clicking noise when you try to start it. The only things that happened before it died was everyonce in awhile when you were driving you could smell burning plastic or something like wiring maybe. And theres been a couple times that while running the dash would kinda surge and the lights would dim and return to normal. Now that does sound like the alternator but wouldnt it still jumpstart? We really dont want to keep dumping money into this car getting all sorts of parts we dont need. Anyone have any ideas or suggestions as to what the problem could be?