Ron,
I have not seen a "starter pack" of metal bars. When I first set up my home workshop, I bought a selection of different size steels and still have some of them. (Never had a use for some sizes after 5 years and a waste of money). It is better to buy the sections that you need for a project as you need them. But if I need some 25×5 flat bar x 200 long, (as an example). I will buy 1 or 2 meters and keep the remainder as stock, knowing that it is a size that I use.
Metal supplers often have off-cuts which are sold at a reduced price. Also second hand steel merchants and ebay are a source of cheap materials.
Paul.