いただきます！ Itadakimasu. I say this before a meal, though I've heard it translated as "Let's eat" to "Thank you for this and every mean". ごちそうさま（でした）！　Gochisousama (deshita) I say after the meal, which I've heard translated as "I'm done" to "Thank you for this meal". I hope this helps! がんばってねください！

ごちそうさまでした。is always appropriate to say after meals. If someone buys you a meal or cooked a meal for you, you can also say ごちそうしてくれて、ありがとうございました。in a polite way. がんばってくださいね(^^)

Gochisousama deshita! ごちそうさまでした This is what you say after meals in Japan. I believe it does translate to "Thank you for this meal." :)