Best Nikon camera for video recording?

So i'm into making youtube videos and i'm gonna invest into a better cam.
Nikon camera specifically.
Which Nikon model is the best for auto focusing when your recording (sitting in front of the camera)?

Nikon does not make camcorders. They make devices that are designed to capture still images and happen to capture video (and audio) as a "convenience feature". You diid not provide a budget. You did not specify what "best" means to you.

I'll assume you want to have you in focus, and the background out of focus"… That is called depth of field. That is done with a combination of large imaging sensor and a lens with a long focal length - and Really good lighting. A pocket camera will have challenges doing that because the lens focal length is not good enough and the imaging sensor is small.

I'll assume that you want "best audio", which is very important for video… Any camera can have a "good built-in mic" when the mic is in the right place to get the audio - but when that happens, the lens may not be in the best place for the video framing. This means that the "best" audio + video framing comes from decoupling the location of the mic from what the video framing needs to be. Many times, this means an external mic (or external audio recorder) is needed. None of the Nikon pocket cameras has a mic input.

There's lots more, but lets stick with just these two items for now. We were just painted into the dSLR or mSLR corner.

Now lets pick a decent d/mSLR that has a decent lens, imaging chip and audio input for the external mic. How about the entry-level D3300. Link to the manual:

http://download3.nikonimglib.com/archive1/Wywwt00lh46s0109T7E089fAaV06/D3300RM_%28En%2902.pdf

Please note that the 350+ page manual has about 10 pages for capturing movies/video. The rest is for still images, software for still images and playback of captured still images (and video).

Lets go to page 155… Easy enough. Be sure to pay attention to the "Maximum length" warning on page 156. 4 gig for an individual file. There's an odd note on page 161 about the "countdown display" that tells you this starts when the camera is about to shutdown and a reference to page 148… Basically, as page 152 tells us, prolinged live view (and video) capture causes the internal electronics to heat up and the auto shut down is the camera's way of protecting itself. It takes a while to cool down.

Also on page 161 is a rather oblique reference to the camera's internal mics recording internal camera noise made by the autofocus lens motor vibration - good thing we were planning for an external mic…

This does not mean these cameras can't capture great video - they can - but they are not a camcorder replacement. If you insist on using this sort of still image device for video capture… My friends who do this have ended up with 2-3 of the same camera so one can be used while the others are cooling off enough to be used.

Since Nikon does not make camcorders, there's no Nikon camcorder to recommend to you.

You will also want a tripod (Davis & Sanford with F18 fluid head or similar Magnus sticks and head), external mic (RODE or Audio Technica) and maybe some softlight kits with stands. Just these three items will get you to about $500. For $300, you can get an entry-level Canon HF R500…

If you insist on getting a m/dSLR, then at least get one that is designed to capture video (and stills are the "convenience feature"). I got a Sony NEX-EA50UH. I understand the Nikon D810 can do a great job with video - and while it has the same file size limitations as the D3300, does not have quite the problems with overheating…