What camera should I start with?

A phone or tablet camera will perform poorly in low light conditions, and have very limited recording time, and no way to connect an external mic. If you're serious about making movies, invest in a good DSLR, and some sort of audio recorder like a Zoom. Or, use an old-school miniDV camcorder. Those often have jacks for external mics, and DV is better for editing than MPEG4 or whatever.

Don't even need a good DSLR to get started.
A Canon 550D goes for about $300 second hand, whack a Rode Go mic ($99) on it and that's a decent start. Wouldn't bother with an external audio recorder until you had something to attach to it like a proper shotgun mic or lapel kit.

You could try a Canon XL1. They are actually quite old, I believe made from the late 90's to '01, but Canon is a very good brand, so I am sure it will still work. I see them going for about 300 - 500 on ebay. 28 Days Later was filmed with that camera. It also uses DV tape, which some people don't like, but I much prefer over digital files or mini dvd-rs (do they still use those anymore?). If you want accessories, you could look up "IndyMogul" and "FinalCutKing" on Youtube, as they have a bunch of tips on how to make stuff and tips on shooting better video.

The answer depends on who your customer is.

If you're your own customer, doing it as a hobby or to teach yourself a trade, you can start with whatever you have, and learn through trial and error what works best for you and where you want to go with it.

If you're intention is to produce cinema style movies and/or work in the "film" industry, a DSLR camera is a good place to start to learn how to pull focus, select prime lenses and do other things that are associated more with film than TV.

If you are interested in photojournalism, sports or other video techniques that are typically called "TV", you can start off with most anything, but will need to get familiar with an ENG-style camera sooner or later. Learning how to shoot smooth shots from a shoulder mounted camera is a skill that's valuable in film as well.