I prefer mine 16 obsidian
Make a rectangle of obsidian and light it with flint and steel
I build mine wit a water bucket and a lava pool like a speed runner
You need a diamond pickaxe first of all, then when you put water over lava it makes obsidian which can obly be mined by a diamond pickaxe, after that you make the portal 4 blocks on the bottom (horizontal) then on the ends of the line u put 3 blocks up (both ends) after that light it up!
First I use 10 obsidian, then I enter the nether and when I return I replace the corners with shrooomlights.
I use 10 then either shroomlight or crying obsidian for the corners
I do 10 to begin with!