I'll try to answer your questions in order:
1. I'm not sure about lights under $100. Some folks here have built their own for much cheaper than what I paid, but I don't know much about that sort of thing.
2. I don't believe that chilis are color sensitive. I've got my plants under a 180w LED Red/Blue spectrum with UV. They're doing great so far. They have gone from seedlings to setting and ripening pods all under the light.
3. how many lights you need depends on the amount of plants you want to grow. Just like the other grow lights, you have to deal with a footprint size. This is basically just the size of area covered by the light. My 180w Blackstar has a footprint of about 3'x2'. I've got 8 plants under it right now. It wasn't bad when they were seedlings, but now that they've grown some, they're really crowded together! That's about twice as many plants as I should have under there. Again I just bought the light to give the plants a good jump start to the season. I had no intention of growing year round. If you are, then you'd probably need more lights or grow less plants.
Do have a look around the site for more info on LED's. A few people are using them.
Neil
