Style wavy indian hair to curls?

My best friend is Indian and has long(mid-back), fine/thin hair. It has a natural wave to it but she normally either straightens it or just ties it back. Since straightening it takes so long, she's interested in wearing it wavy/curly, but since I have thick straight hair I don't have much experience in styling hair like hers.

Her hair is so long (her mother won't let her cut it!) that it's mostly loose big curls at the ends, waves in the middle, and straight at her scalp. We tried to get a more uniform texture - a few friends have told us to put product in it and "scrunch" it - unfortunately, when we made an attempt, the only available product was hairspray. (She's not the product junkie here, you see.) It did work somewhat, so we know her hair CAN create more wave, but she wants to find a good product that will keep wave/curl in her hair for a longer time, without totally greasing it up. Something that prevents frizz without excess oil would be great, too!

A few suggestions I've gotten are Aussie Sprunch Spray, or FX Curls Up, or FX Curl Amplifier..... does anyone have opinions/ideas on what she should try? (She wants something inexpensive from a drugstore) Also, if you know of any other ways to get more texture out of this kind of hair, I'd love to hear them!