Bro - I had similiar stats and history as you (Except I am 4 inches taller), when I did my first cycle.
I did 500mg/Week Sust and 300mg of Deca. I tool l-dex at .25 ed as well. This was a great first cycle for me, as I had a good diet and gained 18 lbs of quality muscle. I did Clomid post cycle and never lost a pound. I actually continued to grow (At a MUCH slower rate) after my cycle.
I would agree with what was posted above about using 500mg. I would not go over 500mg for your first, or second IMO for that matter. I would be afraid that 250 would be enough to shut you down, but not really benefit you that much. Get another 10ml and don't rush into it until you have all your ducks in a row.
Don't make a rookie mistake. Have everything planned out, and have everything in hand before you start. Don't ever pierce your skin with a needle until you have everything, ESPECIALLY PCT products.
Make sure you have a good diet and workout routine planned, and you will see good solid results that will last.