You will have ten lives at the beginning of the game. Every time you start a game in any mode or lose your turn, you'll lose a life that will reload every thirty minutes. If you lose your 10 lives, they'll either reload one by one or you'll have the option to buy them in exchange for gold bars.
You'll also be able to buy packs of lives at the shop and ask your team members to give you lives.
Bear in mind that if you are part of a clan, you'll be able to request one life every four hours, and in order to get it, five clan members will have to help you out.
On the other hand, you can also help clan members that request lives. You will only be able to do it once per request, but remember that no life will be taken from you.