Welcome to the forums.
As for what DCC is best for a beginner, you will need to consider how large your layout will be when complete. If it's a single 4x8 sheet of plywood, almost any starter set will suffice. I have a Digitrax Zephyr that I've had for many years running my N scale layout, and recently acquired a second Zephyr for a small HO layout I'm building.
As for how big an HO layout should be, the only limits are time, space, and money. A 4x8 is a good place to start, many people do.
You're never too old to do something stupid.