https://www.easa.europa.eu/sites/def...20Part-FCL.pdf
From page 224 and on...
In short you need to get PPL A and SEP to be able to gain needed A hours and nice number
up to 100 h is credited. All to be able to make that modular (5) missing ATPL A exams. And than final one...
When my Jr decided to go profi way, my advice was: You need to have A and H at last CPL
and in worst case of lost Class 1 medical Part 66 B1/2 is more than useful for daily bred and butter.
He is still doing this way, now well over 100 f/h on A and H with nice number of Part66 exam done
with approx half of Part 66 on job training done.