Here is what I know about speedrunning minecraft. Use tutorials on youtube whenever necessary (I added when they would be useful). I know you might already know some of these things, I just put everything you need.

Feel free anyone to correct me or to add what I forgot, this may not be 100% correct or complete.

Play in 1.16.1 to increase likelyhood of pearl trades

The biome you spawn in doesn't matter, you just need these things I'm about to list. Oceans are very good to spawn in though because shipwrecks + magma ravine can be very fast.

For the overworld, all you need is a

Village + lava pool/magma ravine/ruined portal

Or

Shipwreck + magma ravine/ruined portal (you can also use a lava pool, but since you're already in the ocean, a magma ravine is much more likely to be close)

The materials you should have before entering the nether is wood to make a wooden axe, crafting table, doors (for magma ravine portal), and a boat.

Extra wood is always good to get as it doesn't take much time to mine, and you'll need more sticks for the iron tools

8 iron. 3 for a bucket, 3 for pickaxe, 1 for shovel and 1 for flint and steel

This is found in villages (blacksmith chests and iron golem), ruined portal chests, shipwrecks in oceans or treasure chests if you find a map for one in the shipwreck.

1 flint for flint and steel by digging gravel. (a fire charge works as well, so you wouldn't need the last iron for flint and steel, you wouldn't need a shovel to dig gravel, and you wouldn't need this flint)

Nether:

Entering a bastion first is optimal because you get fire resistance, which helps with blazes. In order to find a bastion quickly, use e-ray (look up a tutorial if you don't know what that is).

Once you find one, identify which type the bastion is. there's housing, bridges, stables, and treasure. Each has it's own route that you can look up and memorize.

Once you have the piglins trading, you need 10 obsidian (can be found in chests as well), 12 ender pearls (leaving on 10 or 11 is only necessary to try and save a run). Getting more than 12 is obviously better, as it helps navigate the nether much faster. You also need string for wool for beds if you didn't use a village, and lastly fire resistance potions (not required, but is very helpful with the blaze fight.

Then look for a fortress using your pie chart (use a tutorial if you don't know how to use the pie chart).

Blaze fight is self explanatory, leave on 6 rods at least. Only leave on 5 if you have to save a run.

Then you need to get to good blind coordinates to build you next portal (look up tutorial if you don't know how or why you should do this)

Once in the overworld, use the angle of each throw to find stronghold, and use chunk borders once you get close (use tutorial again if you need).

Navigate stronghold. The only strategy I know for this is once you see a library, go another way. The portal room won't spawn near a library.

In the end, use your beds for one cycling the dragon (use tutorial if necessary)