Re: Advice needed on TV pilot
Not getting into length, you have to find a balance between closure (the episode must be enjoyable by itself and, as some colleagues mention above, chances of seeing episode 2 are slim) but this is not a film or a short film, it's a series, so you need to keep your audience wanting more.
However this depends wildly on what kind of series you are making. If it's a procedural, you need to close the story of that episode. What you leave open is all the secondary stories around the characters. On the other hand, if it's a full story (like Stranger Things) you need to open both: characters and plot.