the Chofatz Chaim writes in the hakdoma of the MEshna Berura, that Aliba Dhilchisa should be ones priority.
thats why Orach Chayim should be the first thins one should learn.
teh Shach in Hilchas Talmud Tora states that one is yotze Mitzavs Limud Hatora only by Learning Aliba Dhilchisa.