Car turns over but won't start

I have a 2000 Mitsubishi Galant. Not sure if it is a DE, ES but I do know it is a 4cyl 2.4 L. I bought this car in August and it was sitting in somebody's driveway for 6 years, not being driven. I went to my uncles house on Monday, Oct 17th and he looked at my car for me. He told me my serpentine belt for the alternator was fraying and that I needed to get a new one. On my way home Friday, my power steering locked up and my brakes weren't working so I put it in park. My friend was with me and her dad came and noticed that the serpentine belt was missing. My car would turn over but it wouldn't start, so he towed it back to my house. My boyfriend changed the alternator belt and the other belt (not the timing belt. The one that runs the water pump I believe, unless that is the alternator belt, but he did change both of them) So after he got it all changed we tried to start my car again and it still turned over but wouldn't start. I called my uncle to see what was going on and he said if I've been driving without the belt for a while then it will cause my battery to die because it's not getting any power so I tried to jump my car but it didn't help. He also told me that the timing belt could have jumped time, or the tension was messed up. I've been looking online about what could be the problem. I have no yet checked the timing belt issue, but other people have said it could be a bent valve, or the fuel pump, or that I need to check all the wires. My question is, what should I do? And what seems to be the problem? And it is pretty simple to get the timing belt back in "time"?