Answer to "Is there a spot for a micro SD card?"Some models do, some don't. On a Fire 10 HD there's a little cover on the right edge you can pry open with a fingernail, it's inside that. On other models it may be somewhere else, investigate anything that looks like it might open. But even if it has it, on an Android phone there are some apps that can be moved to SD and some that can't. I did find that having a lot of old pictures (screenshots and from the cameras) eats into the same space available for apps. You can move them to SD with a file manager program, then put the SD in a reader and move them off to someplace where storage is cheap, like a blank DVD.
Answer to "Is there a spot for a micro SD card?"5th generation, sure, but not the original. It's the fastest and most reliable way to transfer files on and off it, shut it down and put a card in or take it out. With ES File Explorer, maybe some others, you can transfer over bluetooth or WiFi or USB but it's slow. I've had a 128 gig card in and out of a Fire 10, works fine.