Crocheted from the top down, with raglan yoke separated into body and sleeves. Sleeves and body crocheted straight. Technique used is typical granny-square, clusters of 3 double crochet sts (US) separated by 1 chain st (3 ch sts at raglan intersections).

Yarn
All kinds of yarn (leftovers or stash is perfect) ranging in weight from fingering to DK, even heavier. You can use one main color and as many contrasting ones as you like.
Variegated yarn works great.
I used 1 skein of Lana Grossa: Mellenweit 100 Color Mix Sparks, col 7614 (100g/400m) as main colour in the sample shown.

Quantity Sample shown (L) weighs 370 g in total
Notions 4 opening stitch markers.
Hook size 5-6 mm, depending on gauge.
Gauge 8 rounds and 5 dc clusters (3 dc‘s separated by 1
ch) make 10x10cm.
Sizes Two basic sizes, S/M and L/XL. The difference
consists in neckline widht and underarm width.
Apart from that, the sizing (width) depends on how
deep you make the yoke. S/M becomes closer to S
if the yoke is shallow, and more like M with a
deeper yoke. Same applies to L/XL. Length of body
and sleeves is up to choice.