becoming a great chess player

Play lots of games.  Analyse the games.  Talk to stronger players.  Read books.  Tactic puzzles are a great training tool for all players, but IMO especially beginners.  The nice thing about tactics is, as necessary as they are, you'll probably also see the most immediate improvement with them.

The games that count are long games, preferably over the board tournament games.   You don't have to analyze every online game, but be sure to look over the ones that were particularly confusing or frustrating.  Stronger players can give good insight into positions that may have taken you a long time to discover on your own.

As for the different aspects of the game.  Tactics and endgames are very important.  Strategy/middlegames are important too.  However memorizing many opening moves is the least important by far, although this is a trap many new players fall into.  It will not improve your game.

It sounds corny, but you get out of it what you put into it.  If you do a little work every day then after many years you'll be really good, there is no magic bullet.