2 footitis happens quite often, so figure out how big you want your boat and add 2 more feet to it! :faint2: Kidding, but not really. It happens to all of us. There is no "right size" or "Right type" of boat for everyone. Before anyone can really help you we need to know what you plan on using the boat for primarily and secondarily. How many people, how often, what type of water (lake, river, bay, ocean), how swift might the water be (currents/tides), do you need it covered or uncovered, overnights, etc. How fast do you want to travel on the water. Before you buy you need to sit down and figure out what you want to do on the water. Since you already own a boat you should have a decent idea.
As far as material for the boat, there are guys on here that will crucify you if it isn't tin and others that will cringe at a rust bucket and it has to be wood or fiberglass. Again, that comes down to usage, size, etc. Each type of build has its pluses and minuses. There isn't a right answer or a one size fits all.
So give us some more info and maybe we can help you out. And there is nothing wrong with used as long as you are careful in your selection.