Clamp lamps are good for smaller tanks because the amount of light they produce are perfect... If you're able to get a glass top for the tank it'd be better, some people say they let out light but they actually let more light into the tank. Excel is a co2 source, so that's good there, but I would pick up some flourish comprehensive which is a liquid fertilizer supplement that will help the plants alot.
Without nutrients the plants will start dying off, flourish comprehensive will supply the nutrients plants need to survive.
I use dry ferts (fertilizers), but I've been in the aquarium hobby for 25 years, and dry ferts cost alot less than liquid ferts. But for beginners I always advise them to use liquid fertilizers until the get the hang of things, and feel comfortable switching to dry fertilizers....
You are on the right track, the best advice I could give you is to read everything you can about planted aquariums, planted lighting, planted substrates, etc... This knowledge will only help you to succeed!!!
