The best seeds in Minecraft for speedruns generate worlds that have resources right away and are near important locations to help reach the End.

Netherite is rare and exclusive to the Nether. To find it, mine Ancient Debris blocks between Y=8 and Y=22 with a Diamond Pickaxe. The sweet spot is at Y=13 to Y=15. Use one of the following methods ...

You are going to need a lot of blocks for this build so you should better get to farming. As for the blocks themselves, you can pretty much use anything. Cobblestone and Wood are the most common ...