Hmm.. if you find that advice from the guide is hard to bring into practice, please tell me what in particular you've got problems with. I might be able to give some advice and update/reword the guide accordingly.
Also it can be pretty hard to get better against people you already beat. However, it helps to think about what your opponents could do, not what they are doing. For example, if they never use side B, but it would be a good move to use, don't do stuff that the move could punish you for. Even if you know they won't use it, focus more on fighting a certain character than a certain player.
And remember basic stuff, don't roll towards an opponent. Sidesteps aren't invincible. Don't forget to mix up your grab game. Defend the edge even risking suicides, it's alright if you end up suiciding a bit in friendlies, it teaches you about what you can and cannot do.