I am an amateur photographer and have recently moved up from a Sony compact (which i had lots of fun with) to an olympus EPL3 which having tried one out on holiday, is a great bit of kit and not as expensive as a full DSLR. There are lots of other good cameras, strobes etc. out there.
However, the thing that really helped my photography improve was going on an underwater photography workshop. Lots of people invest money in kit but never invest in how to use it. I saw two people on a live aboard with the exact same camera; one was getting amazing macro shots and the other had lots of blue piccies. I would recommend you invest in some training. I have done a one day course and have also went on a specialist photographic diving holiday. Worth every penny
