Buy your leather ready to go colour wise, get some dye that matches for the edges to the original colour . Contact Adhesive can be widely sourced . river type ? there are lots of different types , ask the supplier what they recommend for the task at hand ( remember the tools are different types and sizes - for the specifics ) .
Try to avoid purchasing small quantities of leather , its really expensive that way in the long run . Full single shoulder or butt is around £150 but the beast size varies so its done
Wax? Dont actually need it with good leather ready finishe d / coloured. Cut edges you want a product like super sheen for burnishing and antler is a great tool to rub it up
Regards the thin draw bag type leather i have some brown thin stuff i salvaged from an old sofa , if you want some to gey you going?