Necessary:

• Tinkers Construct for 1.12.2 + associated version of mantle
• Minecraft Forge

How to start?

• Just start how Tinkers Construct aims you to start.
• You can see the harvest levels in the descriptions of the items.
• From that point, you are able to mine harder ores and combine them to new alloys.

Hardness of each new Ore in case you gonna ask...

• 2: Tiberium
• 4: Aurorium, Karmesin, Osram, Element Zero, Abyssum
• 5: Prometheum, Duranite, Palladium
• 6: Valyrium, Uru
• 7: Vibranium

Hardness of alloys:

• 3: Triberium
• 4: Fractum, Violium, Tritonite, Ignitz, Seismum, Astrium, Lumix
• 5: Proxii, Imperomite, Niob, Dyonite
• 6: Nihilite, Yrdeen, Nucleum 3
• 7: Solarium, Adamant