Hello, for only one pot I would only put on plant. And that plant would
be a "bush" or "patio" variety tomatoe plant. For not doing any
gardening before I would start with just the one plant. That way when
your eating your home grown tomatoes it will build confidence. As for
the soil, I would use an off the shelf potting soil. No, need to get
elaborate with the soil. As for the window, you really need to see
which gets the most amount of sun. Or just switch windows at noon.
Remember though, tomatoes are not small plants, even the bush variety.