What spices would you put in this?

Well, my basic spices are generally salt and crushed red pepper for a little bit of heat.

If you want a bit of Mexican flavor, some cumin, coriander, chili powder and oregano.
For a more asian flavor, some ginger, lemongrass, garlic, maybe some garam masala.
Either way, a handful of fresh cilantro would be a good addition (on top of each bowl, rather than cooked into it).

Unless I was in a particular "mood" though, I'd probably stick with the plain (salt and red pepper), and just serve it with some cheese toast. :

Greek lentil soup: fakes, pronounced 'fah-kehs'

8 oz lentils
1/4 cup olive oil
1 tbls minced garlic
1 onion, minced
1 large carrot, chopped
1 quart water this is where you could use veg broth
1 pinch dried oregano
1 pinch crushed dry rosemary
1 bay leaf
1 tbls tomato paste
salt and pepper to taste
balsamic vinegar to taste

Lentils in a large sauce pan, cover with an inch of water. Bring to a boil, simmer on medium for 10 minutes. Drain into a strainer.

Heat olive oil in sauce pan. Add garlic, onion and carrot; cook and stir until onion has softened, 5-ish minutes. Add lentils, water/veg broth and herbs. Bring to a boil, reduce heat to med-low, cover and simmer for 10 minutes.

Stir in tomato paste and season to taste with salt and pepper. Simmer, covered, till lentils have softened, 30 to 40 minutes, stir occasionally. Add liquid if soup becomes to thick. Ladle in to soup bowls, drizzle with EVOO and vinegar to taste.

And be sure to try the vinegar, it's really tasty.

I believe I got this from allrecipes.com.

This was from yesterday! And I forgot the potatoes. Agreed, curry powder would be nice.

I've also made a great "North African" lentil stew with sweet potatoes, cumin and cloves and the rest of your ingredients.