I'd just like to note quickly that tasvideos is not designed to host every possible TAS that could ever exist. In particular, its job is to host
1) the best (fastest) TASes for
2) well defined categories that beat the game
3) of games that have entertainment or technical merit of TAS
4) (plus playarounds for games where playing for speed makes no sense and a few other cases)
You are more than welcome to TAS whatever you want, and talk about it/post it on the topic for that game! We love looking at TASes. Just be aware that not all TASes will be accepted onto the tasvideos site itself, because that isn't its goal.
Also, your first TAS doesn't have to be 100% optimal/be the fastest ever. Do testrun TASes, playaround TASes, TASed routing. Look for glitches and tricks other people have done and try to recreate them, etc. Here's what the current real time 'all dungeons' real time route looks like:
http://www.twitch.tv/moltov/c/2251862 If you can recreate that in a TAS, which will require you to find and learn how all of the tricks in it work, you'll be off to a great start in building more skill.