you only need 1 female plant then you can take some clones, try the seed banks and buy some fem seeds, if you try herbies head shop click on pick n mix then choose a fem seed, then you will get 1 fem seed free and 2 regular seeds free, other seed banks have similar offers so check them as well,
herbies free seeds are pretty damn good, this ww x sk i got growing is huge and female so im more than happy, you just need to find a strain you like then you can take clones and have a go at producing your own fem seeds so you have got it for future grows.
the compost i use costs £2 or $3ish per bag for a big bag, i tried paying £20 per bag and it killed my plants and when i transplanted a big plant into a bigger pot with the new compost it turned the leaves into claws and they started to die, so the expensive compost is not worth buying, the
sponsors sell some great products so you could try them, i get mine from the big super markets, its tomato compost and has nothing added to it, you dont want any added nutrients or slow release nutrients, if the compost contains this then you will have problems at some point through the grow, usually at the start but some at the end due to the slow release nutrients giving out to much.
so cheap compost is ideal, you can just use compost on its own but perlite will help with getting more air to the roots, if the roots stop getting oxygen the plant dies as it cant take in water or nutrients, if roots dont get oxygen the roots die and the plant dies, so the roots need oxygen as much as water, so over watering will kill any young plant,