I used to just use one or two covered cake boards to display my cakes on. I've since graduated to 1/2" foam board cut to size and covered. I really like the look of the thick board, but I end up wasting half the foam board. When I cut the sheet, I'm left with small, unusable pieces that are thrown out. I'm curious...What do you use to display your cakes on? I'm not talking some beautiful silver platter for a wedding or anything, just a display board for any regular celebration cake.
Same as you, for two tiers and under, otherwise, I order English style drums. I fancy them up pretty well, whether it is core or a drum. Scrapbook paper, I try to find the glossy surface kind if I can. Satin ribbon, jewels, whatever fits the theme! I try to cut carefully and as close to the edges as possible so as not to waste too much core.
For smallish cakes, like 2 tiers, I put 2 pieces of 3/16th foamcore together & cover those with something pretty.
For very large cakes, I use 1/2 inch foamcore. My sheets are 20x30, so I can get several nice sized boards out of it.
I still feel that it's a good investment. No matter what, unless you always have square or rectangular cakes, you'll have useless bits left over.