I followed Helen Ardley's pattern for a "Snuggle Blanket". I found the pattern in her book "Cute Crochet for Tiny Tots"
READ MY BLOG FOR MORE DETAILS.... http://crocknit.blogspot.com/2012/06/crochet-baby-blanket-rainbow.html
MY RAINBOW BLANKET
Materials: Heirloom/Bendigo Cotton 8ply in 12 colours
I used my stash of 200g balls in each colour.
If you use 50g balls I estimate approximately 1 to 1.5 x 50g balls of each colour; depending on size of blanket, and your tension/gauge.
Size: 86.4 x 86.4cm (34 x 34in) (excluding the edging)
Tension/Gauge: 2.5 fans/shells over 10cm (4in)
The pattern is written in British Crochet terms, but it is easy to follow and easy to convert to US Crochet terms.