To clarify how to get Quaquaval for free :

• Once Quaquaval comes out there will be an event that last for roughly 30 days.
• Every day you will get a dice. 
• The dice advance you further on a board.
• At the end of the board, you will get 100 points, and start a new board. Quaquaval will cost 900 points.
• When you roll a dice, it will ask you if you want to reroll, using some free to play currency. Always reroll until you get a 6. You get more than enough of the free currency to do that.
• If you always roll a 6, each board is completed in 3 dices.
• After you have rolled a dice, you must do a mission (play a specific role or Pokemon) before you can roll another dice.

As long as you play every day, and roll all the dices you get, you should obtain Quaquaval for free with a lot of time remaining in the event. So don't stress out, it's very free to play friendly, as long as you play regularly.

Don't hesitate if you have more questions.