Congrats. You will have fun once you have all your 'stuff'.
Those Besses (assuming it is a Pedersoli) can have varying size bores. They are nominally supposed to be 12 ga. but mine is an 11 ga.
You can get sample packs of wads from Flintlocks, Inc. their website leaves a lot to be desired but you can phone your questions and orders to them.
Finding the proper mould might be problematic. BB owners use different sizes. Mine is a .731. Some use .735, some use much smaller, as small as .715. Try to find some and test before getting a mould.
Use real black powder only. Either 2 Fg. or 3 Fg will work with proper charges.
You can easily make your own scoop or measure from on hand materials.
I do not advise the use of plastic wads, they are not designed for bp. Regular wads work just fine and your gun is capable of good patterns.
Don't forget to buy some extra flints also.