By & large, you can get away with a fairly simple linear supply for vacuum tubes.
In most cases, regulation is not required, the main thing being to get hum as low as possible.
100v would probably be OK for normal "playing about", but a bit more would be useful.
Yes, voltage doublers can be used for higher voltages, & were commonly used in the last generation of tube TVs.(at least in Australia)
If you could pick up a domestic radio with a transformer power supply, you could use that.
Unfortunately, such things are a bit rare in North America, due to US manufacturers' love affair with the "All American Five" type of transformerless radio.
In Oz, those things were commonly known as "death radios"!