ANSWER:
You need to balance your time and try your best to learn a bit from every Branch of sciences. Try to learn the following books:
‘Kitab at Tawheed’ by Mohammed Ibn Abdul Wahab.
‘Beautiful names and Attributes of Allah’ by Muhammad bin Salih Al Uthaimeen.
You can read the seerah (Biography) of Prophet salla Allahu Alaihi wa sallam: ‘Raheeq ul Makhtoom’ (Sealed Nectar) by Sheikh Safi-ur-Rahman al-Mubarkpuri.
You will get the English translation of these books.