Again...+1 on reading Andrew Skurka's book, just to give you an idea about gear. The reading you have done is excellent in terms of how to travel and where...but if you are NOT going to do mostly hostels then you do need more of an education about gear. Not a lot...but some. You'll figure a lot of it out on the road, and the great thing about these kinds of adventures is learning as you go and being able to adapt to what you find.
If you are seriously considering spending most of your time in a tent and cooking your own food, you NEED some practice. It's one thing to rely on hostels and fellow travelers for education...but if you are on your own in a tent you don't want that to be your education.
So. Any recommendations you get here should NOT substitute for your learning at least a little about how to use it...even if that means a backyard camp out. That was a great suggestion.
Bag: if you are going to be sleeping in hostels at all I would recommend getting a bag and not a quilt. That way you can sleep just about anywhere and not have to worry about sheets and whatever slept in the bed before you. I would go with a 15 degree bag...but here the cheaper you go the heavier and bulkier it will be. Get one with a zipper that goes most of the way down, so when it's hot you can just open it up and drape it over you, kick legs out, or just sleep on top of it.
Tent: excellent idea for the SMD trekker. Just buy a pole from them. The point of these shelters is that you CAN use trekking poles (which is what most of us do), but there are plenty of people who don't use them, so most shelters can be purchased with poles. So...just order a pole with the tent.
As for the stove...if you had a ton of experience I'd recommend the whisperlite international which will literally burn anything. BUT...not a good idea for someone inexperienced. Others may correct me - please! - but when I was in Central and South America I found canisters to be rather plentiful. The easiest stove to use are the canister ones - say, the MSR Pocket Rocket ($35). Not the best stove in the world, but cheap and it works. Then get a cheap aluminum pot to go with it. Something I like the Jetboil can only boil water, and on your travels you'll find dehydrate foods difficult to obtain. You'll need to do some cooking, simmering, etc. so avoid the Jetboil.
Don't worry about an external hard drive - way too easy to lose or damage in your travels. Get a cloud account somewhere (Dropbox, shutterfly, something similar) and just upload in Internet cafés when you can. Buy a 16GB SD card for your camera and just upload whenever you can.
As for socks...darned tough are great socks for hiking; I use balega and thorlos for running.
No idea on a cable lock. Look at travel stores online??
Down puffies can be found cheaply all over the place. Not sure where you live, but Costco has a great one for $50. Or you can wait until you need it and pick it up locally.
Hope that helps....