We'll start with the paper , I usually use normal printer paper A4 (297mm / 210mm) 80 grams / square meter thick but sometimes I use other types of paper such as paper wrapping gift.
I know that in some states it is hard to find A4 format but you can use other formats ,it is very important to keep the ratio between length and width of sheet paper, you must have a ratio around 1,4(1,37-1,43) and for this you can cut a small strip of paper to obtain this ratio.
If you want to learn more about 3d origami paper ,here you have a link: 3D origami paper
Here is the tutorial : How to make 3d origami pieces 1.
From this tutorial you will obtain a 3d origami piece just like the left side piece
You can easily see that the 3d origami piece is very sharp and does not look very good ,fortunately there is a very rapid process of turning sharp pieces on the left in very nice round shape piece from the right side.
How to Make 3D Origami Pieces 2
and in this tutorial you can learn aother method to make 3d origami piece and how to keep 3d origami pieces.
In closing I will repeat how important it is to make quality 3d origami pieces, please do not rush learn to make 3d origami pieces correctly and the folding speed of the piece will increase over time with the development of dexterity.You can make this 3d origami piece when: watching TV , on the phone, play music ,you travel.... .