As far as which sativa strain to grow for a fast turn around time I would suggest that you look up Cindy 99 ( C99, Cinderella 99 ). I just finished harvesting some of mine and although it is too early to give a smoke report I can tell you that the buds off of these look fantastic. Sticky beyond anything I have ever harvested befor, and very frosty. The best part is that they finished in 10 weeks of flowering time, which is comparable to many of the indica and hybrid strains that I have grown.
I grow in soil ( fox farm ) under 400 watt hps ( for my flower room ). I don't throw a lot of nutriants to my plants, just what they need to grow healthy. I pretty much stick with flora nova bloom for all my plants + cal mag. As I find that this supplies all of what they require.
Do a google search for where you can get seeds, I have seen them for sale at several different seed companies. ( I got mine off of seedbay ). If I am not mistaken the original c99 was a Brothers Grimm strain that originated from the infamous Jack Herer liniage.

Good luck with your search and happy growing to you