Just taken a breeze through your gallery and you have got some nice bits of work here, however it is clear that that you have some room for improvement. I will be the first to admit I am not brilliant at photography myself so I can only give you the advice I have learnt from my photogrpahy friends. It is clear looking at your photos that you are experimenting with different angles most of which are effective and I think you just need to devlop this more. Try experimenting with adjusting the contrast or colour saturation with your pieces- try experimenting with filters. don't be afraid to experiment- bit may not always look right but you never know you may find something which works really effectively. Sometimes this helps improve the work so it looks more professional. Add borders of white or black to your photos before submitting them here-this will again make them look more professional. Look at other photographers work that you like and then ask yourself why you like it. try encorperating that into your work .
Good luck in the future as you have a really promising gallery