Séries em Inglês Britânico
I don't think there's such thing as "tv shows for begginers" in the sense that they're intended for someone who's just beginning to learn a certain language. I do know some shows like Luther, Sherlock Homes, Peaky Blinders but I'm not sure about their degree of difficulty as far as the vocabulary they use because I've never actually checked them out, but I've heard good things about all of them. As far as whether or not you should use use subtitles, well obviously you should if you're beginner, not only will you not understand much without them but you won't be able to look up the words you don't know, watching tv series is not only a good way to improve your listening comprehension but it also allows you to expand your vocabulary by looking up all the unfamiliar words you come across.
But on second thought I guess there is a specific type of tv shows that is ideal for beginners which is Sitcoms/comedy shows. They tend to not use any kind of technical terms regarding a specific complex subject and just stick to day-to-day casual vocabulary and it's easier to understand what people are saying because the audio is always more clear and there's no background sound effects which can be distracting,however the only one I can suggest is The office in the UK version because it's the only one I've ever heard of. Look up "British sitcoms" and see which ones suit your personal taste best.