Most containerized plants do much better in a smaller sized pot, and drainage holes are a must. There is no way to properly water your plant without the holes. This means that there will be a build up of fertilizer salts (which is the probable cause for the white stuff), and a severe lack of oxygen in the soil system. Oxygen is essential for the continued development of roots.

Sand is really not a good amendment for your potting soil. It tends to pack into the pore spaces, which is the exact opposite of what your plants need. A good potting medium should be extremely porous and coarse textured.

Thanks for your help. So regular potting soil is fine?

Make sure that the potting medium is coarse textured. Adding some bark soil conditioner would be a plus. I'd suggest perlite, but Dracaena sanderiana is among those plants that are sensitive to the fluoride that perlite contains in appreciable quantities.

I've just done some research on hydroculture systems. Do you think this would work well for this plant?

http://www.purlec.ca/howitworks/index.html