One of the delights of real shaving is that you can choose the blade that you like. You are not limited to buying off one monopoly supplier like you are with the mutibladed system razors. Each different manufacturer of blades makes blades which feel and act differently. For instance the Japanese Feather blades are universally regarded as the sharpest, Russian Iridium as the smoothest and many people think that the Turkish Derby give the best all round performance.
Each different brand of blade can be made from a different steel, have a different blade profile, a different metallic coating, a different lubricant, a different surface microscopic structure, and so on. All these elements make a real difference and the only person who knows which is best for a particular shave is you.
Don’t get worried about the choice. All the normally available blades are very good, so anything will do to get you going. For instance supermarket own brand blades are usually Israeli Personna and these have an excellent reputation.
To bring nerdiness to the proceedings and have a lot of fun you can experiment by buying a sample pack. This is almost essential if you are new to real shaving, finding what suits you and what suits the equipment you are using is part of the joy of real shaving. It is your personalised experience. In the UK Connaught shaving are a good supplier of these sample packs, and in America there is West Coast Shaving.
Then once you find the blade (or more likely blades) that you like you can pick them up in bulk even cheaper from the above suppliers or from ebay. They are so cheap that they are best bought in 100s. When you are paying between 5 and 10 pence per double edged (DE) blade you get a real financial benefit over the £2 plus that a single multibladed system razor cartridge can cost. Some real shavers take advantage of the DE blade cheapness to change blades more often, that way they are guaranteed to always have an optimum cutting edge in their razor and on their face.
When you travel abroad you can find out what the locals use. Countries like China, India and the Arabian Middle East get through enormous quantities of DE blades. And Western countries often have strange and obscure brands. Shopping for these and trying them out can add to the cultural experience and adventure of your travel.
Finally remember that what you do is entirely up to you. Real shaving is fun and it is your personal experience, so do what you want. Ignore everything I write if you want. You are in charge.