Here is my strategy:
1. Learn the mechanics of the game. Don't worry about how to use them, just understand them.
2. Learn your moves, including normals, one by one. By that, I mean that you must learn until subconscious what will happen with each button press. Don't worry about knowing the correct use of the moves yet, just know all the moveset, and a faint idea of their range, speed, etc. by heart. Shouldn't take too long.
3. Now it gets fun! Learn universal offense. By universal, I mean everything that is not match-up specific. This is for all situations were you are in control, and your opponent is reacting. Since you are in control, you have freedom of choice, which is why I recommend learning offense before defense. Learn your characters mix-up, general wake-up, etc. Everything that hardly changes from situation to situation, or character to character. Now we are talking mastery, not just learning. This will take a while. Remember, we are only talking things that are largely mechanical, that don't require you to think ahead or improvise.
4. With the above, learn and master the appropriate combos that the prior-mastered strategies will let you land. Will take long.
5. Universal defense. Learn how to "generally" deal with fireballs, zoning, command grabs etc. This is when you are reaction to a controlling opponent. This is learning, not mastery. Mastery will come when we start focusing on match-ups. Since it is not mastery, it should take less time than 3.
6. Match-ups and specific situations: this is the biggest and arguably never-ending step. Learn the match-ups, and specific in-game situations, starting at the most common and working deeper and deeper. By that, I mean that you should start off learning how to counter character-specific bnb for everyone and then move deeper, instead of isolating a character and trying to master fighting them at once.
This is every specific situation the game may present. How to react to every single conceivable situation, frame by frame. Both with character specific moves or system moves such as advancing guard or what have you.
6. Putting it all together: a more abstract, not really conscious step, mainly about having a gameplan. With your new knowledge, you should know before the game has even begun whether you will be aiming for keeping your opponent on the ground, or staying away from them, or etc. It's basically just having a notion of what the game will look like in your head before it begins.
Of course, you will dip your toes in all of them, especially 5 and 6, over time, otherwise you wouldn't ever get close to practice your offensive strategies in step 3.
Remember, everything you do should follow pre-planned flowcharts, outside of randomness in mix-up and etc (which is calculated randomness)., and reaction stuff such as movement.