hey man, welcome to the forum first things first, mixes get posted in the djing forum, not the production forum, no one will reply to you here if you post mixes.
I did however listen to your mix as it stirred a little nostalgia (seeing Netsky play out made me want to start mixing ) and will reply this once
did you use turntables? cdj's? laptop? if you used one of the first two then its not too bad considering its your first mix, fairly simple transitions with almost no blending but at least the tunes were fairly synched.
listen to more dnb, dont mix one producers tunes its far too samey, also 30 mins is sort've the minimum sortve set you should aim to record
learn about eq blending and double dropping (check out the dj'ing forum)
practice, practice, practice!
I really enjoy mixing, it is such good fun, I am not getting to bad now either. (Click play on the soundcloud player below my post if you want to hear a mix of mine )
I would also like to know what you are mixing on man! I am going to hazard a guess you are using a laptop this being your first mix and all? If so I strongly suggest getting your hands on a Midi Controller to plug in to your laptop or computer, I am using a Hercules. If you use one of these you have the advantage of being a little bit more hands on and can then move on to dropping out lows, mids and highs during the mixing of two tracks, which I notice isn't happening in your mix.
So, overall nice mix mate, just keep mixing loads and loads Another important thing to do is make try out new tracks or genres so you can further your skills a little more I started out mixing D&B but I believe House Music might be a good starting point. Of course, if you have no interest in that just keep mixing whatever you fancy!