How to Insulate Crawl Space
I sorta like spray foam, but I don't like the DIY "kits" which come up to 600 board feet per kit, typically. It's a long story involving the technical details of pro foam installed with a heated hose and (expensive) foam proportioner, vs. the refrigerant-driven approaches like Tiger Foam, Dow FrothPak, Handi-Foam, etc. (my problem has to do with the GWP of the propellants, if you're interested).
Anyway: it can be quite hard to get a foam applier to install a tiny job (or even return your phone calls!). If you simultaneously want them to spray your attic you might sweeten the deal, but it's the most expensive insulation in any case.
Reflectix is fine, as long as you don't believe basically anything they say about it. The EPA, I think it was, tested such insulations under slabs (where the manufacturer DOES recommend them: radiant barrier under a slab, ha ha!) and found they amounted to an R2 or so, as I recall. They would be a fine draft barrier but for the challenge of installing them tightly. You haven't described your perimeter crawlspace wall, you could make it a partially-conditioned crawlspace (insulated the side walls, vapor barrier on the floor, toss in a dehumidifier, and bob's your uncle): that has a lot of advantages.
Combinations of foam board and small spray foam cans used thoughtfully (propellant: isobutane GWP 1.0 vs. 1200+ on FrothPak) can make for a tight install. In any case it's probably worth putting a vapor barrier down on the ground, to reduce moisture in your "dank" crawlspace: even in crawlspaces with "adequate" ventilation, natural ventilation relies on wind and other air movement -- it's a bad (if common and legal) design.