There are two schools of choosing a memory card:
1) A single, large one
2) Many small ones
A single one is easier to carry (if it is large enough you basically forget about it during the entire shoot (a great benefit!)) and have enough space for a few movies as well but small ones are both faster and safer (if one malfunctions you still have some pictures).
Which card to choose? It depends on your willingness to shoot video. If you are only a still photography shooter, get a larger cheaper card or a few smaller ones. If you want video, you will need a large and fast card. Currently I am using a SanDisk Extreme 32 GB card
High Speed SDHC Card - SanDisk ExtremeŽ SDHC? Cards | SanDisk and it works very well - no problems with the highest quality video setting.
For comparison, my backup card is PQI 16 GB Class 6. It allows to shoot only about 20-30 seconds of video before stopping due to lack of speed of the card. For stills it works very well though.
For me 32 GB is the smallest capacity I would buy (64 GB would be better but it is just too costly!). The problem is the video, not stills. For stills I think 16 GB is plenty. Those figures are for a single day of shooting - I upload all "keepers" to a computer at the end of each day.
The reader is really not that relevant. I am using a Lexar Professional Dual-Slot Card Reader and I must say that I would not have bought it again. It works but I just expected more for the price. I think any middle-priced model will be perfect. In short - spend the money on a card(s) and not the reader.
About the battery - I have both the Pentax one and a cheap brand one and I must say both perform equally well (maybe Pentax is slightly better but the difference is insignificant). I see no reason to go for the original Pentax one.