Where for a tube-newb to start?

One of the challenges is to find new tubes that have the character of the grail vintage tubes. There is a thread elsewhere here on Audiogon about the rectifier the OP wants info on- and various comparisons among users who have tried different new tubes. For that tube, I am using a Mullard first series fat base, which is one of the grail tubes, but even these aren't the kind of crazy money that some tubes fetch. (And I have a stash of other old rectifiers for this slot, all of which sound different in my particular piece of gear).
Ultimately, a lot of people use tubes like tone controls, to flavor the sound to their liking, within a given piece of gear, within the context of a particular system and listening bias. The whole notion of tube rolling is, in some ways, experimentation (subject to using the proper tube that is a correct equivalent). Unfortunately, as TBG said, some of the most desirable old tubes fetch big money.

The Cable Company has a pretty good selection of tubes. They'll give you recommendations for which tubes will work best for you.

Let me take a stab at providing some useful info. As a start, GZ34 and 5Ar4 are different designations for the same tube. It is a rectifier tube. The most popular old tube from the glory days were Millard GZ34 tube made at the Blackburn plant in England. Good ones are hard to find and expensive. A very good new production tube is the Gold Lion 5AR4. They go for about $40.

Is this the kind of info you want.

Brownsfan- you were one of the active participants in that thread I was referring to about the search for a new, readily available rectifier.

That's a nice little amplifier - mostly point-to-point wiring, about 25 watts per channel. You should be able to do some tube rolling with it. There are a variety of EL34 tubes, and you might be able to use KT77s as well, which could give you a little more extension top and bottom. There are reviews on Dagogo, Possitive Feedback and Six Moons. I agree with Brownsfan, despite his questionable taste in football teams, don't discount the importance of the rectifier tubes. They definitely can have a positive effect on the sound.