A 45mm tilt-shift lens and a good solid tripod would be a great starting point.
Lighting is next, but a lot can be done with ambient light, reflectors and flags.
If I were buying lighting today, I'd seriously consider some of the fluorescent continuous "cool" lighting that's now available. These aren't your standard household CFLs... but color balanced and stabilized bulbs made specifically for photography.
Various sorts of flash or strobe lighting can work quite well with various light modifiers, but is more difficult to visualize and set up. Continuous lighting is easier to set up, but for many decades only "hot" lights of various types have been available. They draw a lot of power and put off a lot of heat, so are less practical for many purposes.
Cool fluorescent lighting opens up new possibilities... best of several worlds... Lower power consumption, less heat, yet continuous and easier to set up. Shooting digitally, the color of lighting is less critical than it was with film. It's easy to set a Custom White Balance and/or tweak image color later in post processing.
Let's clarify one thing... Small diffusers such as those used on portable flash are not all that great. They are still too small a light source. On the other hand, a big soft box on a powerful strobe or continuous light is another thing entirely and - used right with fill lights, other lights, reflectors, etc. - can give you tremedous control over light and shadow in your images.