Reddit mentions of Remote Shutter Release Cord for Canon EOS 5D, 50D, 40D, 20D, & 10D Digital SLR Cameras

From my list that would be THIS

This would be a great add-on.

my favorite dinosaur is a Velociraptor. Those things are bitch'n.

First do as others have suggested and make sure you understand how it is supposed to work to focus, if you find it is not always working right the switch in your camera could be broken. You can get one of these to test it: https://www.amazon.com/gp/product/B001G9TYHE/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
If that works all the time your button is broken, I picked up a used 5D and had similar weird intermittent problems then it totally stopped working, I took it apart and found the first piece of metal in the two stage switch had broken, it can be fixed but it requires taking basically the whole camera apart, my camera works great now.

• Gorillapod- really cool and fun to use (My uncle's friend actually owns the company!)
  
• A prime lens is definitively a good idea.
  
• You probably don't need to get a fancy remote shutter, a simple one will do (I use a 10 dollar one that I bought a few years back)
  
• you can never have too much memory!
  
  EDIT- I failed at bulleting