Welcome to Lit.
Being a "great dom" means different things to different people (as does being a "good sub"). It's often kind of one of those life journey sorts of things. I'd advise against getting instruction/influence/perspective/training/etc from ONE person. Yes, you may learn how to be a "great dom", but you'd only be learning that person's views of D/s.
Read old threads; start new ones. Ask questions. Don't restrict the kinds of advice you're open to hearing. Think about what attracts you to D/s... when you visualize the ideal D/s situation, what does it entail, and what do you need to do/learn to make it happen?
You mentioned being married, but looking for a "good sub"... she might be right under your nose (your wife).