Therapy dogs don't require specialized training. I think attending training classes is always a good thing, even though you can do the training at home. Classes are great for working around distractions and you have someone experienced to take a look at your technique and make constructive suggestions. I don't remember where you're located, but in the US there's a Canine Good Citizen test that's a good place to start. It may even be mandatory. After that, I would contact one of the organizations for therapy dogs like Therapy Dogs International, Pet Partners, etc. Even though some places might not require you to be part of an organization, I think it's a good idea just for liability purposes, particularly if you want to work with children. Here are a few links for you that might help.
https://www.akc.org/sports/title-recognition-program/therapy-dog-program/therapy-dog-organizations/
https://www.tdi-dog.org/About.aspx?Page=Getting+Started
I can't help you much with showing. I don't know if it's the same in all breeds, but in boxers it's pretty political. Or it used to be. I did consider showing boxers at one time and I even had someone that would mentor me, but after seeing how many veterans on the show scene behaved to newbies I decided it wasn't for me. That was quite a few years ago though, so I hope things have changed. I guess I would suggest visiting every show that you can and trying to find someone that would honestly evaluate Ruger and maybe be willing to mentor you if they feel he's a show prospect.