Tubes are fun.
It’s adventure and a pathway like one of those mystical books. What I did was read about the most admired vintage tube amps and bought those on ebay, and then sold them on and got different ones. I think you should start with el34’s or 6L6 amps. Learn about how they match with the components you have. And then think about the fact that some of your components might not play well with tubes.
Oh I thought about a big caveat here, I like a very vintage tube-y sound. A lot of people here like tubes that are much more modern sounding. That is not my taste, so you might find out where you land in this world. There are some tubes, the ones that are more powerful, that often sound like a slightly warmer non tube amp. That is not my preference, I want a thick, slow, big tube sound with a beautiful midrange blume. To each his own.
One more thing, most of the vintage amps aren’t amp and pre together. A few are and there are good Chinese amps that are. Anyway, I find vintage tube amps and horn speakers the most enjoyable (and visceral) end of our hobby.