Personally, I think Liu Yao, Bazi and Feng Shui are the most practical. So we say one fate, two luck and three feng shui.
But the easiest thing to learn is the Six Yao lines, and the hardest thing to learn is the Bazi, Feng Shui and so on.
The easy-to-count information of plum blossoms is not as stable as the six-yao line, so many people who have learned plum blossoms still use the six-yao line.
The Six Yao is easy to use, and it can be used to test everything. You can directly use the Six Yao to measure Feng Shui and luck, as long as you have good skills.
Personally, I feel that if you want to learn, it is best to start with Six Yao. It is easy to get started and the learning cycle is relatively short. No matter which one you learn, as long as you learn it, it will be practical. Some teachers I know are so good at horoscopes that they rarely use the six yao lines. They can use the horoscopes to see the major events that happen every day.