You need ONE starting battery and ONE bank of house batteries. If you mix different types and different "aged" batteries with new ones, you will shorten the life of the new ones.
If your starter battery is good...then it can be kept on "Battery 1" then you should build a new house bank of a size determined by your AMPHOUR needs and if you are not full time cruising, the batteries should probably be wet cells rather than sealed AGM's or GELs. You also need to consider your charging system (alternator and dockside) when designing your battery bank to make sure they are sized right for your needs.
Figure out your needs using the spreadsheet link here:
http://www.semarine.com/store/home.php?cat=87
Then come back and chat about what you should do and how to wire it all up. BTW...welcome!