I have just completed my 19 stars top after booming near to 20 tops. Note that this is not a post to show off. I want to show that I am really doing something not hyping something, you know that people can just say that they enhanced a 20 stars fafnir bow without proof right.
Here is what you need to do if you really want a 19 stars weapon or armor, this is what I found out, you need to boom near to 20 quantity of armor or weapon to get 1 19 stars weapon. This is what I have tested out and it is true.
Most of the maplers will stop at 17 / 18 stars as they don't think there is a need to go for 19 stars at all. But this is wrong, 19 stars boost a lot! From 18->19 stars, I gain about 12 wa. With the 4 19 stars equips above, I gain near to 50 wa comparing it to 18 stars.
This is my advice to all the maplers who want to yolo, keep going, don't give up, your day will come. Trust me, if you boom, get 1 more, just keep going. Tell yourself that you only need to get it once right and that's it!