I have decided to order a combined lathe/mill from an Italian manufacturer, it seems ok to me they they assure me they have had nothing but great reports back from their clients.
It is a fairly cheap machine and it's principal use is not neccessarily gunsmithing. If it turns out that I can also manage good work on it for gunsmithing then so much the better.

Now I need to know what toold are going to be useful.

All I have at the moment are some end mill bits and a few cutters for the lathe.

Can anyone give me some advice as to what kind of tools I will need? thanks.

Without knowing what your projects are going to be I would say, right and left handed turning tools, a parting tool, a facing tool, threading tool, a small .187 boring bar with carbide inserts (Circle machine) would be a good start. These are the tools I use most and all use carbide inserts. I have a ton of other tools for specialized work, but until you get some idea of your abilities and what direction you plan to go, the above listed tools will do you fine.

Milling tools, you should probably have some end mills ranging from .0625 to the maximum shank size your machine will take. For instance, if your machine will take a 1" shank tool, then on the top end of the list, I would have at least a 1" mill. You can get large fly cutters and shell mills for machining large surfaces, but until you know what you and your machines abilities are, and where you're going, Keep it simple and think Carbide.