Your first 15 iron ingots
Allocate your first 15 iron ingots: 3 for a pickaxe, 3 for a bucket, 1 for a shield and 8 for a chestplate. You also need planks for the shield and sticks for the pickaxe. A full suit of iron armor costs 24 ingots; making the chestplate first avoids waiting for the whole set. Reference: Minecraft: first steps.
Build a shelter, place a bed and a chest at the spawn point. Plant the vegetables or seeds you find, leave ready-made food for returning for things. This reserve is more important than the second set of decorative tools.
Five diamonds and an entrance to the Nether
Make a pickaxe and an enchanting table from the first 5 diamonds. Prepare 14 obsidian: 10 for the portal frame without corners and 4 for the table. The table also needs a book and two diamonds left behind.
Take flint and steel, food, nonflammable blocks and one piece of gold armor into the Nether. Gold pacifies ordinary piglins, but not piglin brutes. Your first route is for blaze rods and nether wart; do not risk all your supplies in one expedition.
The food yield and supply of planting material are calculated in the manual: A reliable food supply: crops, animals and travel rations.
From blaze rods to the stronghold
One blaze rod crafts into 2 blaze powder. An ender pearl and powder make an eye of ender. Thrown eyes help locate a stronghold, but can break; the portal frame may need up to 12 eyes. Bring a reserve beyond the expected count.
Before entering the End, leave a bed and spare equipment in a chest at the stronghold. Sleeping sets your return point in the Overworld; a bed inside the End explodes. You can enter immediately, but cannot freely leave through the same portal before defeating the dragon.
Crystals, phases and retry are described here: Your first Ender Dragon: preparation, crystals and a battle plan.
