Everyone has their own taste, and with slide films the opinions seem to run exceptionally strong. I don't see what people like about Velvia except as a "special effect" film, but obviously lots of people see those colors and absolutely love the result, so there you have it. To my eye Provia 100F looks very natural *in* *sunlight*---it can go really blue, really quickly, in the shade, and I usually shoot it through an 81B filter to keep that under control. But basically I think this is a "jump in and try something and see what you like" situation.
In my understanding, the contrast of a film and its latitude are intrinsically correlated---I mean, the steeper the characteristic curve is, the more an exposure error changes your results, right?---so you would expect that of the Fuji films, Astia is the most forgiving and Velvia the least, which might argue for starting with Astia. However, my experience is that you can get away with fairly sloppy technique with Provia and still get acceptable photos. I've shot a fair amount of it in old folding cameras whose shutters are of dubious accuracy, and done OK.