[quote=Awson]
Is this good advice or terrible advice? Can't tell.
[/quote]

She's being sarcastic. Normal people don't start off being good at something (there's a reason terms like "child prodigy" exist -- they are aberrations). Everything is an acquired skill and practice makes perfect. You're not good at building decks right now but if you keep doing it, you will be eventually. Just like everyone else at the event who beat you. It's their experience building decks in general, not their (lack of) knowledge of the specific cards that were used, that mattered.