Showing up every day to do whatever the latest events are makes a much, much bigger difference than paying a ton of money. So yes, you could play the game and eventually be competitive without paying any money. If you buy the monthly pass for $5/month, that helps quite a bit. But pouring hundreds of dollars into the game will help you a whole lot less than you might guess at first.
For what it's worth, I've won daimyo twice (server-wide weekly tournament) while having only paid for the monthly pass and less than $32 in other stuff, nearly all of which came before the monthly pass existed. So you don't need to be a whale to be competitive, though you would need to show up every day, not just now and then.