All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
In general, seeking knowledge is a religious obligation; however, learning certain fields of knowledge is a communal obligation (required of some Muslims only), while learning other fields is an individual obligation (required of each and every Muslim). We have previously elaborated on this point in fatwa 15872.
As you mentioned, our website is a rich source of useful knowledge in various fields, so whoever searches it for what he needs to know about religious matters will find plenty. However, he may not find all that he needs, in which case, he may find it in any other trusted reliable source.
You asked, "I am confused whether reading Tafseer of Quran and books on Tawheed and ʻAqeedah separately is obligatory or not?" Our answer is that it is not an obligation to search for the information in the original source for it; rather, it is enough to seek it in any source that has a sound foundation.
It should be noted that one of the best ways of acquiring knowledge is to study at the hands of a scholar who would guide the seeker of knowledge through a progressive educational program, clarifying the general indications of the texts and problematic aspects and explaining the odd scholarly views to him. In addition, the seeker of knowledge thus acquires the refined manners that are the adornment of scholars and seekers of knowledge from him.
Allah knows best.