My main priority is getting iron gear. It provides enough protection that you can survive most hostile mobs.
I had trouble doing that with diamond armor. Stupid creepers....
After that I go for diamonds and an enchantment table, preferably with full bookshelves. Then I cycle the 30 level hint until I can guarantee Fortune 3 on a Diamond Pickaxe. Then I do diamond mining. I use those diamonds to make armor, and I cycle the enchantment hint until I can guarantee Protection 4. Then I use enchanted books to improve my armor pieces.
How do you get to level 30? I think the highest I've managed to get was around 16. Then I got killed by a stupid creeper....
Along the way I try to get a mending villager so I can keep my powerful weapons and armor intact.
What is a mending villager? I don't think I've ever seen one of those....
I know you tried to answer my question, but now it raised more questions!
I suppose the first thing I need to do is try and get a mine together to find coal and iron, then see where I can go from there.
"All the miseries and evils which men suffer from vice, crime, ambition, injustice, oppression, slavery, and war, proceed from their despising or neglecting the precepts contained in the Bible." -- Noah Webster
My blog: Writing from Idaho