I've got a plant that was from bagseed that is about 5.5 weeks from sprouting and i still can't see for sure if it's male or female because those parts are so small and can also be mistaken for new leaf/growth. So basically, it takes time. Usually people have a plant "veg" for 8 weeks from seed. that means put on all it's growth BEFORE the budding. You want all that growth so you will have more bud sites ;)
Somewhere between week 5 and 8 you will totally be able to tell. I added a pic of male preflowers from my first seed and female preflowers from my clone. Both plants were ready to flip to flowering (done in veg). These guys let me know who would make bud and who wouldn't. Read up more and you'll get it :)
Males= balls/pollen sacks
Females= white hairs sprouting from calyx