Whether you're a new or older player, you're bound to have times where you're in need of money. This guide will help you learn how to earn some moolah! :)

However, these things will take time and patience. You can't expect a POOF, and suddenly, you're rich. Patience is the key to games like these!

Silver

Silver is the main currency on the game, and can be used to buy pets, items, and many other things. Some ways of earning silver:

Daily Quests
Quests are one of the easiest ways to earn money. To go there, the tab is between "battles" and "explore", or you can click here.
Each day, you recieve 5 quests. (This can be increased to 7 if you have an Embassy building) Each quest will have a requirement and a reward. If you have a pet that fits the requirement, enlist it for that quest! In 4 hours, your pet will be returned and you will recieve the reward.

Explore
Explore is another great way to earn money. You can find a lot of money on islands! Although you generally find more money when you explore with pets of higher levels, all pets can give you a good amount of silver in time.
The explore tab is between "quests" and "trading", or you can click here.
There is currently no player guide for explore, but if one is made I'll update this.

Buying/Selling Pets and Items
Pets generally sell for a minimum of 500 silver. If anyone is selling for anything less than 500, buy it and sell it for more! You can also grab one pet a day from the pound. It's a great way to earn money.
To sell a pet to a specific buyer, go to my pets (pets > my pets), select the pet you wish to sell, and click "sell pet", which should be on the right side of the pet profile.
To put your pet up in the public sales, go to trading > pet trades, and click the create lot button at the top of the page.

Items are also worth a decent amount of silver. Although I cannot give you an estimate of what items are worth, I can say that items from the premium store are usually worth more than other items.
Also, I advise you to never buy any items from the state store. Most of these items are highly overpriced and you can find them from other players for much cheaper.

To sell an item to a specific buyer, go to your warehouse (inventory > warehouse), select the item you wish to sell, select "sell" from the dropdown menu, and specify a quantity.
To sell an item in the public sales, go to trading > item sales and select create lot at the top of the page.

Sending pets to the pound
You get 500 silver for sending a pet to the pound. To pound a pet, go to your pets, click the pet, and select "send to pound" on the right side of the pet profile.

Posting in the forum
You get 10 silver for every post in the forum. However, do not spam.
I wouldn't rely on this to earn money, but if it really works for you, go for it.

Breeding Offers
Players can earn money by offering breedings from their male pets. Not surprisingly, the better the pet's genes are, the more their breedings will be worth.
To send a private breeding offer, go to the pet's page that you want to breed with (the pet must be female!) and click breeding offer, which is on the top right corner of the pet's profile.
If you wish to put your pet up for public breeding, go to their profile, and click breeding offer on the top right corner of their page. You can also go to the Trading tab > Breeding offers or click here. There is a button at the top of the page that says create lot.

Gold
There are currently only 4 ways to earn gold in the game. It can be spent on items in the premium shop.

Referrals
Referring a player to BK with your code will earn you 10 gold. However, before you recieve your gold they must finish the tutorial.
To get your referral code, go to My Account > Refer a Friend, or click here.

Weekly Charts
You can recieve 10 gold every week one of your pets places in the top ten in the weekly charts.

Reporting Bugs
Found a bug? Report it here! If the issue is an actual glitch, you will recieve some gold, the amount depends on the bug you've reported. You can also report typos here! You get 10 gold for every typo report.

 Real Money Purchases
Gold coins can be purchased with real money here.

That's it guys :) Thanks for reading!
If I made a mistake or you want me to add something, feel free to let me know. Also, if you have tips for earning mony (exploring with pets with certain genes, buying/selling certain things, etc) feel free to post them here! 
I hope this guide helped you! Enjoy the game.