Whilst using a DE my first soap was Col Conk, probably Bay Rum. My first soap was probably from the VDH kit at walmart. Went with Col Conk because it was 'cheap', now anything under $15 is cheap and anything more is worth it.
I am loathe to throw away things that are usable, you should see my area of the house, so I will not throw away products that others might. The first soap I finished was from a soap maker selling the soaps on ebay. First ingredient is olive oil so you know how poorly it lathered, second soap I completely finished was VDH amber which lathered better but I could not really say I liked it better, working now on a cake of modern Williams, getting good lather with a boar brush and taking my time to load and then work the lather and I will keep using it until it is finished.
I only have about 20 more soaps to work with after this, I had SAD the first year of wetshaving with a brush. It will be a couple of years before I will need to buy another cake of soap.
I've finished off tons of cans of Colgate, Gillette and Barbasol aerosol shave cream. I have also finished off a puck of Col Conk, a few tubes of Erasmic, a puck of Calani, and I'm well on my way to finishing a puck of Dr Dittmar off within a month.
But mostly, I buy it, try it and sell it without finishing it off. I'm pathetic.