To grow Dragon Fruit (Pitaya) from seeds is easy:
Just buy one dragon fruit (or even more, if you like to eat them) and get some of the seeds inside - they have thousands of them.
Put them on a kitchen towel (paper), let them dry for some days and plant them in soil (or even leave them on the paper). Water them and cover them in the first time with some cellophane,
so they don't get dry. That's all - after they start growing (and almost every seed do so) put away the cellophane and water them if ever necessary. Not to much, but also not to less - they also
like, if you spray them with some water from time to time.
I am not sure, what temperature they need for growing. Here in the Philippines it has always in between 25°C (min.) and 35°C and it seems, they like (see the pictures below).
If you cannot buy a dragon fruit in you local area - you can also order dragon fruit seeds online.
There are different
kinds of dragon fruits: Yellow, red fruit with white flesh and red fruit with red flesh. Additional to the seeds, what I got direct from a ripe fruit, I also ordered some online, and they are
same growing (even it seems they grow a little bit slower, but maybe I am too impatient now).
The first months, they have been growing very slow, but now they start growing really fast (look at the pictures).