Need suggestion for long female hair.

Schulpting hair is fun!

You might try rooted hair (give any old blond Barbie a haircut)--seeing as how Moonstone wears a helmet (at least the incarnation I'm familiar with), it'd be easy to hide the rooting job seemlessly. Aside from looking more realistic, rooted hair has the benefit of not impeding neck articulation.

Sculpting hair isn't too bad, get the general shape you want roughed out, then go crazy 'drawing' the lines of the individual strands into your clay or whatever you're using. Multiple hair lairs usually looks better than a single one, but you have to be careful not to bulk it out too much or it looks fake/wiggish.

How bout some Marvel Legends Shea Hulk hare?

Well you know what they say: Practice practice practice. Could go get some non-drying clay and just practice on a random head to get your technique down. Thats what I did and I'm much better at it now than I used to be. Just a suggestions. It's kind of a pain to track down decent premade hair IMO.

I haven't had very good luck sculpting long hair.

Danger girl Natasha had some decent hair. Not removeable though. Could always sculpt your own, then you get exactly what you want.