From listening to to Decibel to Don't Be Silly it sounds like you have a good idea of cueing, beatmatching etc but the 2 tunes are out by half a beat, they aren't aligned...
Killers Don't Die back into Don't be silly is a lot better but they are just slightly off... Once you get 2 tunes locked they will still drift a little bit.. just make sure you are constantly monitoring and making little adjustments
Again, Original Ninja into Stingray was a bit rough because it went out, as with a few other mixes.
Key points are
1. Make sure you are really really familiar with the basics - cueing, when you drop in, counting the bars, you obviously have a good idea you just need to practise loads
2. constantly monitor & adjust
3. don't get fed up and pack it in, keep at it
Def a good effort and much better than i was after only a few weeks, good stuff mate!
If you haven't seen it already i'd recommend looking at Ellaskin's tutorials on djtutor.com:
http://www.djtutor.com/dj_tutorials.php?subgroup=mixing&pagename=mixbasics
Explains all the basics really clearly, and you can just keep watching & practising, n unlike having a mate teach you it won't just fuck off when you run out of skunk :p Although he mostly mixes house & techno, all the principles apply, there are 1 or 2 dnb videos on there as well, as well as of course tons of help available on the one and only dnbforum!