You can pay to get things done more quickly, but you don't have to pay to win. It just takes more time. From what I hear from players of the game, there's no actual gameplay advantages locked behind a paywall, only cosmetic items. They obviously want you to pay to proceed faster, but it doesn't appear to be like some games that make free players use lower tier weapons and items. You can earn all gameplay items through grinding it out and never need to spend any money.