battery problems

Started out with what I thought to be battery problems so I changed battery it cranked but after one day I noticed battery getting weak so I assumed alternator bad , changed out alternator charged battery and then had nothing. Lights would work but nothing else would not crank or even turn over. Kept fooling with cables and finally it cranked. Now nothing else works turn signals, tack, a/c, blower all nothing. Head lights and radio are all that work. I removed pos battery cable with it running it killed it so now I'm totally confused. I desperately need to fix have spent money I didn't need to spend and don't know what to even look for now. If you can give any advice it would be greatly appreciated. Thanks.