Welcome to the forum Esme.
Now I only play the PC version, so I can't really answer the question on importing Sims from your studio.
As for the question on gems and scrap, I'm guessing that these would behave much the same way across the different platforms (someone with an XBox will hopefully correct me if I'm wrong). In the PC version, there isn't a lot to do with gems and such beside getting them cut (or smelted if it's a metal) and then selling for a higher price - generally cut gems are worth more than uncut ones. There is also the option for tranfiguration - do you have the display case that can be used for that on the XBox? Here is a link to the
guide about transfiguration.
As for the scrap metal, yes that is used when using the invention bench. It is also used when sculpting in metal (if you don't have any in your inventory, you can click on the inventing bench to buy scrap).
I hope this helps. As I said, this is how things are for the PC version, but I'm guessing there isn't a lot of difference.