Seeds: As said, you are not guaranteed a female even with feminized seeds.
I have started to growing 3 or 4 of a strain at one time, thus massively increasing the odds of a female.
If I remember my statistics, with 4 seeds there are 5 possible outcomes with 4 seeds:
1. 4 Males
2. 4 Females
3. 1 Female, 3 males
4. 2 Females, 2 Males
5. 3 Females and 1 male
So, there are 4 outcomes with at least one female. So, with 4 seeds you have a 4 out of 5 chance at least one plant will be female.
When I started ( And I'm still a noob, even though I have gotten a few plants to flower) I was using one seed per strain, thus chance was 50:50 and of 8 plants started, only 2 were female.