Sometimes it's not about the right or wrong smoothie because we all like different flavours. You might have tried the same basic flavours for so long to the point where you're getting bored.
What you should do is experiment slowly with interesting ingredients like salt, fresh mint leaves and vanilla essence until you come up with your unique smoothie menu.
But, remember to make small changes at a time so you don't end up ruining a whole batch.
This step is essential because the wrong move might give you a gross texture. If you're following a recipe suggestion and it recommends that you chop something into small cubes first or blend your ingredients in a certain order, it's better to follow that.
Also, don't assume when it comes to the number of ingredients you should add. You can start with what is indicated in the recipe and then customize it later.