I usually recommend finding something that's 'about' a subject you're interested in - it's a great way to pick up vocabulary. So, if you like sport then there's Jonathan, for example. Or if you're into gardening there's Garddio a Mwy (not sure if that's still on at the moment, but it might be on Clic either way), or the one Aled Sam's been doing - Gerddi Cymru, or something like that?
I used to really enjoy another Aled Sam one, 04 Wal, which is basically nosing about other people's houses. It's going back a few years now but there are sometimes episodes on Clic. There are some brilliant documentaries available as well.
But one of the benefits of S4C having to cater to the entire Welsh-speaking population is that there's an example of just about everything on there!
I get that you were asking about the level of the language, but just watching anything will help even if you don't think you're understanding it - honest! I watched S4C with subtitles for a couple of years before I even started trying to learn, and I'm sure it helped the language wheedle its way into my brain.
Another tip is to watch the news - either after you've watched it in English (so that you know more or less what is coming up), or before you watch it in English (so that you can check whether you've understood it!) The newsreaders generally speak very clearly and intelligibly.