I don't think 50g will knit a scarf unless it's for a child. You'll need at least 100g for a scarf for an adult. Some of these 'frilly' scarf yarns are sold in 100g balls but the one I used (flamenco) is in 50g balls so would need 2 balls. I used size 5.5mm needles. The shop ought to give you a leaflet on how to use the yarn when you buy it.

cheers
Hazel