You should study and use general opening principles, because they are more understandable and more practical. With time, you'll find out certain move variations that you play well against different opponents - chances are they'll be "book" moves of some already studied opening, and you may have a look at it for some information and ideas. Vice versa - you may check an opening that leads you to bad games so that you may find what's the reason. But don't try to memorize moves you don't understand and don't play such moves too. Opening theory has been created as a summary and analysis of chess openings, it is their consequence, and it is based on opening principles and move choice mechanics, and if you study/practice/understand them then you'll be fine enough with opening theory. Don't bother about learning book variations unless they help you.
is it really that important to follow chess opening theory?
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Opening theory is good if you find that you oftentimes blunder early on, because you overlook a move.
Around 1200 though, the difference between 1. e4 and 1. f4 isn't game-breaking.
Nope. Study tactics.
And endgames.
First of all let me clear i'm not a professional chess player. I was pretty confident about my game couple of months ago, but after that I started to follow opening theories, and to be honest I don't have that much source to find reason behind a particular move in a particular opening. So I just followed but wasn't too successful. I never played it professionally.. But whenever I played I was great with unconventional move, specially attacking move. There are few players. whose rating is a 2000+, against whom I had good record.. But since when I started to follow these theories i'm really struggling, in fact I'm struggling against 1200 player sometime. So my point is should I go back to my own style or should I give more time to study all these theories. Thanks!