Ok then, just use Vue 5.

Make a procedural terrain.  Dig all around it flat leaving a spike or two in the middle. Add to your spike if necessary.

Now, take the clipping slider and move it to the right till you have a stalagtite. Save it as a .vob and follow the other steps above.

As for materials, there are any number of ways to do it but....

...it would be very helpful if you posted an image of your project so others can actually see where there may be issues.  'Not looking like an actual cave' doesn't help us help you very much. No offense meant...it's just easier if we can 'see' where you are having trouble. Please post one so we can get you squared away....

If you make a terrain for your cavern floor and ceiling, you can use the underside of the terrain if you choose 'skin only' in the upper left in the terrain editor.  Just a tip.

Also...how much Vue experience do you have?  Are you new to the tool?  That info will also help...