I just received the Sylvania 7 inch tablet for X-mas, it says for a lot of the applications I need to add a micro-sd card, I've never owned anything like this, I have a 1 gb micro sd in my phone for pictures, but want to get a 16 gb for this, and there are so many, and I have been reading about the different classes, since this is a tablet, and not just for pictures should I get a more expensive one? I'm on a desktop pc, and know nothing about portable devices.