first is test. I would get your levels checked. See what your test levels are naturally. As we age, tehy decline. So check that out first. Then as for cycling, you can do a ton with just test. I would start there. 4-500mg EW with adex to control estrogen. If you have found that your natural levels are low, there will be no need for PCT if you decide to do hormone replacement therapy. Then from there, I would consider a second cycle of test 500mg EW with Mast200 at 300mg EW and adex of course. These would be good cycles in genreal, especially for a 50 yr old. I have worked with many guys in your age group and these cycles have worked well. Some of my coolest transformations have been in guys your age that have never cycled gear. Then they decide "Screw it. I'm going to get in shape for the first time in my life. If I dont do it now, I might not be able to". Well heads up, with the right hormone levels, you can do a LOT. So get in there and get it brother :) 

Let me know if you have more questions. We had tech issues and I was away for a month, but we are up and running again. I should be caught up with all the current questions in the nexxt couple weeks. So from there, I will be able to respond to you more quickly