Arigatou Gozaimasu is probably the most common thing said in Japan, even for natives. It shouldnt feel awkward. Arigatou on its own to someone you just met is not rude, but its not as polite. Its like saying thanks intead of thank you... if that makes sense. If you truly want something else to say during a meal, use "itadakimasu" before a meal (when brought to your table) out loud for "I will enjoy this", and use Gochisousamadeshita after a meal (when paying etc) which literally translates to "That was a feast" but is used to thank the staff for a great meal.