Regarding the SSD and HDD: better get 256GB SSD first, and install OS on it. HDD can be easily added later, and because it is best to have OS on SSD- it is faster and far simpler option than later transferring OS from HDD to SSD. Also buying 1TB is not very cost efficient, it is best to buy 2TB for ~$10 more, or bigger drive. Bigger drives are also faster. Toshiba statistically have much lower failure rate than WD and Seagate- and HDDs are the PC part that fails the most and makes it hurt.
RAM: I'd go for 2x8GB at once. Ram is cheap these days, and mixing ram later can cause complications or hurt overclocking.