Is this a good deal? s/c miata content.

https://portland.craigslist.org/clk/pts/d/miata-jackson-racing/6740897465.html

$1500 bucks, Jackson racing kit. I’ve never bought a used supercharger before, so learn me before I make a bad day...

You'll want to confirm what engine it's for as that will determine what brackets, etc come with it. That's an M45 supercharger, which was just the right size for the original 6 psi application on a 1.6. It's undersized for making any real power, but it's a nice simple install if you just want 30-40% more power. They can have some driveability quirks.

I'd peg that as the high side of the value, I would have expected closer to $900 or so but it's been a long time since I looked at used ones. I sold one 12 years ago for $1200.

I bought one two years ago for $1200, then sold it a year later for $1200.  For a street car, they add some power and can give you some fun.  I wouldn't even consider it for a track car; they make tons of heat, and have some reliability issues with belt slippage/breakage.  The timing box that it comes with is OK for 5-6 PSI; you'll also need a rising rate fuel pressure regulator too.

After going down that road: IMO long run for a short slide.  

My usual recommendation is to enjoy it for what it is and don't try to get more out of it. They're just plain tapped out.

That blower, with brackets and pullies and throttle body as appropriate, would fit either the 1.6 or 1.8, however I see no pullies or brackets in the picture.  Good tensioner pullies can be had for $200 off the shelf from track dog but you'll still need to fabricate mounting brackets (for the blower and throttle cable) if they're not hiding at the bottom of that box.  Also pull the top of the blower off and check condition of the vanes/coating.  

I bought a $900 setup including better engine management, all the brackets, and crappy homemade pullies about 1.5 years ago.  Personally I'm not a big fabricator so the missing brackets are a significant pain, and the pullies and/or engine management are a significant additional expense.  Some couplings are missing too.  Basically I think a ready to go kit is worth $1000-$1500 and they seem to trade hands around that price, depending on quality of parts, but this one appears to be VERY FAR away from 'ready to go'.

In that price range, I'd be looking here:

MKTurbo

That $1500 will get you the whole hotside for a Miata.  Chinacharger, but they're getting good results.  Another $500 for the intercooler and piping if DiY is not an option.