Ok... forget DECA. Do some test, 500mg is more than enough. Even 350 to 400mg is a good start. Add some 500mg Primo or/ and Mast for the final touch. Do it with some anastrozole to keep water out and control some other sides from strogen. You need to do your cycle based on the competition, you cannot stop it one month before the comp just like you said in Shadow's forum... no,... you need to do the whole cycle based on the physique you want to achieve on the comp day.
There you said something about using hgh on pct and pre comp... actually, we use to drop hgh days before the competition, sometimes, a week or couple weeks, some can do it with hgh, but they reduce the dose. You'll need to do some diuretic to look like "stage mode", using steroids you'll not be able to drop the water without diuretic. You'll need to drop testosterone too... but it will depend on your physique and how you carry water.
To compete natural is actually easier than with anabolics... As a natural you can drop water without diuretic and don't need to think about everything I told you... you should research more and maybe do steroids with help of some trainer, just because you want to compete and you want to do it right. I think you'll not be able to do your first cycle for a competition based in what you told us... you need to learn about steroids reaction in your body before you try to compete, or do it with some closer help.