Eltab
Lord of the Hidden Layer
I make notes during the game session if we discover something I want. Price for certain, and description if available.When I take valuable treasure (art, gems, etc), I usually record it on my logsheet as follows:
GP + X (where X equals my character's normal share of the treasure); GP - Y (where Y = the value of the art object, or objects). Then in my notes section I record something like the following: Treasure - 500gp gem (-500gp).
I record +X GP as assigned by the DM, then immediately buy the ring/art/gem/whatever. This is how I carry around "37 GP, 25 GP green gem, 10 GP trade bar"
I also carry around a few things of no apparent value that we found along the way, such as "coinpurse full of gold-painted wooden disks" (which I carry plainly visible so somebody can Pickpocket IT instead of my hidden-under-my-shirt coinpurse of real coins).