If you have not try before enchaning to 19 stars, I will say that you don't try at all. I wasted a total of 20b+ on my fafnir hats (boomed like 6 pieces of 18 stars fafnir hats without getting 1 19 star fafnir hat.
The pain of getting a 19* is more than 20b+ ... and the cost of getting 18* is way lesser. Maybe in 2b you can get a 18 stars. 19 stars is crazy.. from 18->19 stars you will keep failing and failing and in the end you will see a BOOM!
I have gave up on getting 19 stars on my fafnir hat and topwear. Although I managed to get my fafnir pants to 19*. The cost of getting a 19 stars is very very crazy.
If you are unfunded, go for 17 / 18 stars. Don't ever try 19 stars! Don't even try 20 stars! Trust me you will regret if you go for 19 stars!