First player need to build [[Coating shrine]]. This multiblock open access to some new material, most useful of them for know is lava-coated still that allow player upgrade their boilers.
Mv opens access to aluminum for aluminium bronze and infernal alloy. Also mv circuits, which combined with infernal alloy required to make [[Infernal boiler]], first steam producing multiblock of [[GregTech True Age of Steam]]. Player would also need [[Cooling box]] to cool maintenence fluid that is required to get infernal slug and process it into purified infernal dust.
[[Infernal boiler]] can and should be upgraded with better coils and better power hatches on the way, as it boost power production greatly.
Infernal alloy also opens tier 2 of single-block steam boilers. At this phase they are probably quite useless, but suppose to have some niche uses.
HV is supposed to be a huge Age. First and most important material is probably a conceptualized steel, that can be used to craft [[Concept Infusion Matrix]]. You will also need infernal circuit to craft it.
[[Concept Infusion Matrix]] opens access to crafting concept catalysts which allows to craft plethora of different metals.
[[Industrial gas pressurizer]] is the next in line. Infused with compression concept, this machine allows you to compress steams into their dense variants. This transaction usually leads to volume loss, but with some compression strings and perfect conditions it can even lead to volume increase.
[[Spawner extraction machine]] allows player to harness spawners and build automatic farms from it. This multiblock also provides better infernal slug and blaze source. And also opens second tier of water - [[Hellish water]].
[[[Industrial coating line]] is direct upgrade from [[Coating shrine]], finally fully automatable coating method.
At this age player also can upgrade [[Infernal boiler]] with beating husks so boiler can produce [[Critical steam variants]].
Heating cometal also used to create tier 3 of single-block boilers.
[[Regulated Cryo Chamber]] is somewhat upgrade from Vacuum Freezer. It provides EU-free paralles and speed boost in continuous crafting.
[[Cooling tower]] is direct upgrade from [[Cooling box]], which is just 16 times better in terms of cooling capacity and its aggregation speed. Also 10 times faster.
[[Geothermal plant]] is another mutliblock for steam production. It is much smaller, consumes less power and supposed to be less picky then [[Infernal boiler]].
[[Gas burning plant]] and [[Fuel burning plant]] is counterparts to [[Large Gas Turbine]] and [[Large Combustion Engine]]. They suppose to burn gas or fuel and consume water to produce steam, providing slightly better fuel efficienct then just burning everything directly.