Noni is a Hawaiian "canoe plant," that is it made the voyage here with the first Hawaiians. It's easy to grow if you're in Hawaii. It needs full sun/partial shade and is drought tolerant when established. Any good garden soil will do. The fruit is stinky like cheese so don't plant it near your house.

An excellent, comprehensive book on noni has just been published by authors Scott Nelson and Craig Elevitch. It's called "Noni: The Complete Guide for Consumers and Growers." Good luck.

Here is a link that might be useful: Noni: The Complete Guide for Consumers and Growers

Aloha!
We used to live on a noni farm and this wonderful plant grows anywhere at all - even straight out of lava rock. Start them small in a mound of soil held upright by a plastic rim, then cut the rim off in a year when they take root well. You don't need to water or fertilize them. They are quite strong. Remember to prune them well each year or they will get too tall to pick fruit from the top. Usual spacing is about 4-5 feet between plants.

If you google "noni, propagation" you will get all the data you need. They are easy but the seeds need some preparation to get germination in a reasonable time. Without it it takes longer.

They are easy to grow in nearly all lower elevation areas of the islands.