No, that's a fine way. Right now it is more important to improve at the game than to have a repertoire.
But consider to Write down 'what you know' so you keep a record and don't have to invent the same move over and over again. A repertoire imply to have some kind of record of what you play. It can be written (what I prefer as you can easy ad explanations), it can be in pdf or some database, or it can be in an opening book where you ad comments in the colums.
A repertoire normally means that you at least know what your first move will be as White and you know what to play as Black against 1.e4 and 1.d4 (+ your reply to the most common answers).
At some time a special opening sequence will begin to irritate you because your score is bad and/or a lot of the players that you meet plays it. Then you sit down and study it and finds a way to play that suits you. Then you are beginning to build your repertoire.
I don't really have much to add that isn't already in the title. I'm really just asking how I should go about building an opening repertoire. So far my method is just playing what I know and, when I run into a different line, study that. Is there any other way to go about it?