The gold and gems are closely related and, to some extent, mutually dependent on each other. The main difference is the difficulty of accessing them. Gold is easier to get, while gems are a premium item scarce for free within the game, so you have to buy the gems for real money most of the times. You can also fill out surveys to get credits from Google Play and get a good handful of them with little effort.
Gold is the basic currency and it serves to buy new cards or improve the ones you already have. If you are part of a clan, you can earn new coins just by donating some of your cards to the team. Depending on whether it is a common, special, legendary or epic card, this will be the cash reward you receive.
If you have not yet reached enough level to join a clan, there is no choice but to fight and win battles. It is the only way to win gold in Clash Royale, which is surely not the easiest one.
For its part, the gems come out of the coffers you get when you win. They do not always come out at all, but it is quite common for a few, enough to accumulate. The advice is that you do not waste them in the first levels, because you will need them when you face more powerful rivals.
To earn gems fast at Clash Royale is to take a look every day at the proposed accomplishments and complete them. For each of them, the game rewards you with the gems or gold.
The usefulness of this currency is mainly to open chests faster. If you do not use the gems to speed up or cancel the countdown until you can open them, you will have to wait several hours and even more than one day at times. To earn the gems, you can get more information about Clash Royale gems by crhackz.
As you ascend through the different levels, the difficulty increases. The rivals are experienced and most probably know all the tricks to configure the best strategy of Clash Royale in addition to having good decks, so you might have to modify your tactics to adapt to the circumstances.
In addition, as in each level you unlock new cards, those that served you in the previous arena can stop doing so in the new ones. This is because in addition to decks there are anti-blows, specialized in countering the strength of some cards or decks which is usual among the players. However, with a lot of effort you can make your way by knowing what you have and when and how to use your cards.