Furniture as in tables and chairs and things, for dungeons? I'd go for styrene, or matchsticks & coffee stirrers, first.
If not, or otherwise, my first thought is Privateer Press putty, which is Polymeric Systems brown/aluminium, AKA ye olde brown stuff. It takes sharp details and edges a little more easily than green stuff and procreate, and sands and carves much more easily. (For getting those angles down) At the same time, before it cures it's got a kind of 'chewing gum' texture like those other two; as opposed to claylike putties like milliput, apoxie sculpt, magic sculpt, etc. Those take details, sand and carve easily too (more easily) but have a less elastic, more 'granular' consistency* which can be somewhat friable for small details. Like, say, thin chair legs at 15/18mm(?) At least until you get to know how to work them.
But right out of the packet, with little experience, for the job at hand, my personal first choice would be brown stuff. YMMV.
Second choice might be Tamiya quick type. Elastic before curing, hard and rigid after. Quite nice to use. Tends to be more expensive than other putties, but might be on a par with BS in that regard.
* Not to say they're gritty, but they'll tear and crumble if pulled, rather than stretch.