It is great you want to do something about your weight. I did also and it was one of the best things I ever did. I started at around 133kg and I am now down to 79kg, it took just under two years (with a lot of ups/downs and back/fourths in that time - it could be done quicker also).
The key to losing the weight is lifestyle changes and you are doing the right thing by joining the gym and exercising.
The most important bit to get sorted now is your diet. You should post it up and let people give their advice. You could lose weight quite fast with the right diet in place.
Then once it slows down you can look into supplements and stuff, but you could easily lose most of your weight now with a good diet in place (which is further increased by working out).