As you contemplate the task of moving from Scripture into systematic theology, please consider the following warning from Irenaeus about how the heretics known as the Valentinians distort Scripture to support their ideas. Note that Irenaeus is not against systematic theology; rather, he is against imposing an unbiblical system upon Scripture; he prefers to allow the “order” or “proper connection” of Scripture to assert itself. As we know, this is a perilous but necessary task, and this is why we should be constantly reading Scripture and hearing it, letting its order and proper connections form our theology. (Taken from Irenaeus, Against Heresies, book 1, chapter 7, in ANF, volume 1):
Such, then, is their system, which neither the prophets announced, nor the Lord taught, nor the apostles delivered, but of which they boast that beyond all others they have a perfect knowledge. They gather their views from other sources than the Scriptures; and, to use a common proverb, they strive to weave ropes of sand, while they endeavour to adapt with an air of probability to their own peculiar assertions the parables of the Lord, the sayings of the prophets, and the words of the apostles, in order that their scheme may not seem altogether without support. In doing so, however, they disregard the order and the connection of the Scriptures, and so far as in them lies, dismember and destroy the truth. By transferring passages, and dressing them up anew, and making one thing out of another, they succeed in deluding many through their wicked art in adapting the oracles of the Lord to their opinions.
Their manner of acting is just as if one, when a beautiful image of a king has been constructed by some skilful artist out of precious jewels, should then take this likeness of the man all to pieces, should re-arrange the gems, and so fit them together as to make them into the form of a dog or of a fox, and even that but poorly executed; and should then maintain and declare that this was the beautiful image of the king which the skilful artist constructed, pointing to the jewels which had been admirably fitted together by the first artist to form the image of the king, but have been with bad effect transferred by the latter one to the shape of a dog, and by thus exhibiting the jewels, should deceive the ignorant who had no conception what a king’s form was like, and persuade them that that miserable likeness of the fox was, in fact, the beautiful image of the king. In like manner do these persons patch together old wives’ fables, and then endeavour, by violently drawing away from their proper connection, words, expressions, and parables whenever found, to adapt the oracles of God to their baseless fictions.