Ideal cross section for insulated floor on posts?

What is your ideal or favorite method to insulate a floor? Preferably very well insulated and using more natural materials?

I have an old shed that needs some work. This is a decent sized shed maybe 20x30 with a short second level for storage. It is up on posts. There is no insulation other than some cardboard boxes staples to the walls way back when. The roof leaks and it's starting to sink on a couple corners. It needs some serious work. I have all sorts of good ideas for the walls. I'm pretty good on how to jack it up and fix any support beams, but I'm a bit stuck on how I should insulate the floor. Should I just put insulation just between the supports and not care about thermal bridging? Should I add a layer of insulation sheets (those 4x8 sheets from various materials) between the supports and the floor itself? Add insulation sheets to the bottom? It's on posts, but not really tall enough to bother with any kind of skirting around the outside.

The structure looks something between timber framing and stick built for what its worth.

A photo would help!
Which floor the elevated one or  another.
Walls would love some batts.
The only natural effective insulation is wool, I have used seaweed but it settles ad its effectiveness is reduced.

This guy has a few videos detailing his use of metalic bubblewrap insulation in simlar circumstances:

Note that a considerable part of bubble foil's insulating ability comes from reflective surfaces. A shiny surface like this bounces heat back from either direction, entering or leaving. The same factor applies internally, as heat does not easily emit from one surface into the bubbles and bounces from the other surface back into the bubbles. Especially for floors, a layer of bubble foil suspended, not touching anything on either side more than it must for fastening, will give the best possible performance.  The video's installation directions actually negate part of the material's effectiveness,though for retrofitting it is probably as good as you can do. Putting down 3/4 inch or so of battens before laying the bubble wrap would let it have a reflective surface on the bottom as long as it doesn't touch the subfloor too much, and natural draping would give a slight reflective gap on most of the top surface. Adding even 1/4" battens above would improve that.
If you don't want to add on top of the floor surface, fastening the wrap to the bottoms of joists or between them will also work fine.

Here is a good overview of its properties and correct use.

Yeah, I think his technique is effective enough, but the airsealing might be as big a factor as anything.

I wonder if you could layer builders plastic with sheets of cardboard, right ontop of the floor.
On top of that  old carpet, for traction.

Air sealing certainly could be a factor, though on a plywood subfloor there will be extremely little air leakage to start with. In other locations it would make a real difference.

I know many modern builders suggest air sealing, (which I agree, is probably one of the primary ways that the foil bubble stuff works), but I am not a fan of that style of building. Too easy to get mold. And this is at the base of a hill. We had quite the stream coming down from the melting snow and rain running right under this shed... until the kids had fun redirecting it around the shed and down across the lawn and to the driveway. I now have a rut in the lawn to fix and a ditch about 10" deep running across part of the driveway... but the kids had a lot of fun in the water, I think it was worth.

Anyway... that was the long way of saying, it's really wet, so I prefer to use methods that allow for drying from any direction. I use to say breath-ability, but I have heard enough people argue that that is not a very specific word when used for walls/floors/roofs. Mineral wool, hempcrete, cob, etc. I don't want humidity to get stuck somewhere and cause problems.

I think rockwool batts held inplace with window screen and hardware cloth would insulate well, drain well, and discourage rodents or insects from making nests.

To combat thermal bridging, you could glue 1.5" wide ×2" thick battens of  ridged insulation along the bottom of each joist.
This would  effectively make the joist deeper and insulated, but still allow you to drive fasteners into the wood to support window screen and hardware cloth.

Now that is an interesting idea. Adding a support extension made out of insulation could work for thermal briding. And the screen/hardware cloth idea sounds good too.