Currently everything in the game is available and accessible to a free player. You do not have to pay for any content. However, as suggested above, enhancements to gear/weps is available thru the in-game Item Shop. Be aware though that the currency used for Item Shop (Diamonds) can be traded/bought/sold for gold, which is the game currency. As such yes, you can grind gold, use it to buy diamonds, and then buy directly from Item Shop. I personally have never spent 1 cent in the game and I can run some instances end-game (with guildmates help obviously). Nevertheless, though, yes it does take a lot of time and grind. Spending money does indeed help tremendously but I wouldn't go as far as to call it "Pay2Win". Some items yes, they are only exclusively available through the item shop and can only be used with diamonds (item shop currency) but as I said earlier, they can be bought freely with in-game currency. I would advise to get acquainted with all the different types of currencies in the game, at the moment I can think of 9.
Diamonds-Item Shop Currency
Rubies-Item Shop currency that can be acquired as a bonus when you spend Diamonds (has exclusive items not even available with Diamonds)
Gold-in-game currency
Phirius Tokens- Item Shop Currency by doing daily tasks (quests) <--- some of the basic items can be bought with diamonds or tokens
Phirius Shells- currency obtained when doing daily minigames that can be farmed for stats (attributes that enhance gear)
Energy of Justice- currency obtained doing regional events that can be used to buy stats as well and some other gear
Mementos- currency obtained from doing instances (raids) and killing bosses. Can be used to obtain even more stats and gear
Proof of Myth- currency obtained from killing world bosses with can be used to obtain the best stats in-game and gear (orange stats)
Honor points- currency used to buy pvp gear, materials to donate to guild, mounts etc
Have fun using them lol if you do decided to try the game
, I'm pretty sure there's probably at least 1 or 2 currencies more.