It doesn't come with a micro SD card. The internal storages on Galaxys are often called with names like "sdcard0" though, so it might confuse some people.
I have a 32gb that I bought for my Droid 4. I would go up to a 128 when I can afford it. I like having the space. I also put TV shows or movies on my card to watch at lunch. I also have music and other items on there.
I like using the basic "My Files" app. I can find my videos to watch easily.