Not gonna lie, bo3 is way harder than bo1.
I'm super new to game, and in gold. I do fine-ish (think 50-60% wr) in bo1, but bo3 is just so much harder. You're going to play a lot more control decks and you're going to play completed decks. No one is running 4x garbage card instead of what was in a deck that went 5-0 in a competition. The quality of the deck is just way better.
Latest 5-0 decks if you're curious as to what the meta kind of is.
https://magic.wizards.com/en/article...gue-2019-02-07
For the curious, I'm running an izzet drakes deck. My lines are bad, and I still don't know all of the cards/costs in the meta, so I play into a lot of dumb sweepers or counters.