If it's anything like World of Tanks or World of Warships it should work like this:
Battles will earn you Silver, XP and 'Free' XP.
Silver is used to buy vehicles, repair vehicles, any new modules you unlock for them things like that.
XP is used to unlock vehicles and upgrade modules for purchase, if you're on Vehicle A and want to get to the next one in the tech tree you'll need to play Vehicle A to get XP and unlock vehicle B.
Gold is a for real money currency which you can use to progress faster by converting the 'free' xp into normal XP to spend. You can also buy premium vehicles which should in theory earn more of everything but isn't advisable for new players to look at until they have more time in the games. You can also buy premium time which will mean you earn more xp, silver, free xp. You shouldn't need to buy any of this if you don't want to, it will just take longer to progress.
Again I don't know what Warplanes is like compared to the other two but usually once you get to the higher tiers repair costs mean having premium account makes it easier in that you're earning more silver so have less chance of losing silver if you die in a battle.
If you need more detail it's probably best to check the official forums, reddit or a youtube guide as I don't think this game has a huge following compared to the other two titles.
