I'm pretty sure you won't find a strain where you "can see good results in 30 days!" At the very least your gonna need to sprout a seed and veg (6-8 weeks) and then flower (6-8 weeks), so your looking at a total of 12-16 weeks before you see any results.

If you get lucky and get some clones then you can cut out 4-6 weeks of the veg cycle, so that's 8-12 weeks for results.

As for seed companies I have always used Seed Boutique (formerly SeedsDirect) and Nirvana brand. Really good genetics for the price. Especially good for beginners. They have a wide selection of varieties.