This is a User Guide to gaining free 
without having to buy them with real cash.
#1 - The Invited Players Feature
If you have invited friends who are starting out with the game, you'll get Gem Rewards based on their Level Progress from the Invited Players feature on the Social Menu. You can only add Invited Players who have just started the game and have not yet reached Level 10. But because the Friends Directory doesn't cover Level Progressions, it makes things harder to get Gems without knowing wat level that which friend is currently at. To understand how to get Invited Players and to learn how to get more Gems through this feature, please read the Gem Earning Advice section, seen in the "Invited Players" article itself.
But unfortunately, nobody seems to care about the Invited Players Feature as the article itself has been completely ignored.
#2 - Derpy Hooves
There is a chance that when you click on Derpy hiding under her box that she will spawn a among the 
she usually pops. The chance is approximately 30%.
There is no limit to how many times you can click on Derpy in a day, so long as you can find her. She can be easier to find in Canterlot than Ponyville due to the fact that the area is smaller and you would have less buildings there. While there is no set pattern to her hiding, after 3 or more taps you may find she spends time wandering around talking to other ponies instead of hiding again. You can try closing and restarting the app to trigger her hiding again. This trick no longer works starting from update 3.3 as Derpy now spawns only once per day.
#3 - Clearing Parasprites/Changelings/Bats/Vines
Sometimes when you defeat the living obstacles called parasprites, vampire fruit bats, changelings, or forest vines, you will be rewarded either some , a , or occasionally nothing. You will need five shards per set of parasprites or per changeling, and three shards per set of bats. For the vines, shard amounts vary depending on the size of the vine. As you tap on these obstacles, will sometimes be rewarded. The last tap may cause a to be rewarded. If you are tapping one of the larger Snapping Vines, you may receive an extra gem prior to the last tap that defeats it.
The Everfree Forest also has one Cragadile in each of the (two) swamps when they are first uncovered, which are defeated in the same manner and also reward coins and the occasional gem. They do not respawn.
When you expand your Ponyville/Canterlot/Sweet Apple Acres/Everfree Forest map areas, Parasprites, Changelings, Bats, or Vines will usually appear. The type of obstacle depends on what level you have reached. Please note that no more than five of the obstacles will appear at one time in the three towns, so do not expand an area of darkness until you have defeated at least one obstacle, to increase your chance at receiving a gem. If you are clearing dark areas around the edges or corners of a town, more than one area will potentially be cleared simultaneously (bonus!), so be sure you have removed enough obstacles before clearing. For example, the upper left corners of Canterlot can spawn three changelings by clearing one area of darkness. (This is particularly useful during a Solo Event!)
#4 - Balloon Pop Games
Friendship Balloon Pop
Once you have bought all the ponies that require 
, there is not much else to do with other than play balloon pop with them. There is a chance that you can get either 1 (uncommon) or 2 (rare) from a balloon.
For those people just starting out with only a few friends, struggling to get even the first pony, they may not think they will ever reach this stage. But it will happen. Check out the Friends page, and put your name there for others to add, as well as checking links for other "Add Me" locations. Be sure to add your name to the Directory and add friends from the list as well.
If you really want to earn a lot of Gems from the Heart Balloon Game, save your hearts until your certain desired amount is reached. Currently, it is unknown how many hearts you can collect until you've reached the limit.
Equestria Balloon Pop
There are additional Balloon Pop games that can occasionally award gems. The Equestria Balloon Pop is a free game, but only playable once every 24 hours, with no skip option. Gems may be awarded in amounts from one to three. More than one gem prize can be won in the same round, although it is rare.
Clear-Sky Balloon Pop
The clear-sky version costs 3000 bits to play and resets every three hours. Rare prizes may include one, two or three gems.
Royal Balloon Pop
The Royal Balloon Pop costs 20 gems, so is not likely to be used solely for earning gems. While trying to win rare ponies, however, gems may be awarded in amounts from one to three. GameLoft once had a special promotion, however, where they offered a very difficult chance to win 500 gems in the Royal Balloon Pop.
#5 - Feeding Shrines
Harmony shards eventually cap at 999. To avoid wasting shards, go to Ponyville and tap activated shrines. As you feed shards to the shrines you will get a whole lot of bits popping out. There is also a chance that a single will also come out for every 100 shards fed in. The rarer the shard, like Magic, the better the chance. The average chance rate is discussed on the harmony stones page. Laughter shards have the lowest rate, about one gem per 900 shards. The game remembers how many shards you have entered, sort of like a bank balance. So a gem may be returned after a session of spending just 100 laughter shards, if two prior sessions to earn bits used up 400 shards each. It seems every 1000th shard guarantees a gem, provided the location isn't reloaded (no traveling to other towns, no entering any mini game, pony editor, zecora's hat etc.). You can obtain 1000th shard from shops.
To speed up the process, zoom in all the way on the harmony stone to spend shards more quickly. This makes it easier to avoid tapping on earned bits which will be collected automatically. Locate the stone in the bottom left corner of your screen if you tap with a left hand finger, or in the lower right corner of the screen if you tape with a right hand finger.
#6 - The Crystal Mine Game
Playing the Crystal Mine Game will grant . are granted as rewards after collecting enough minecart points. If you're really good at the game you can eventually pick them up during the game itself, just like element shards. After a certain amount of points no new gems will be available as reward - only coins and element shards.
A tip for getting minecart wheels is to go around and tap each of the trees in Ponyville or anywhere and they have a small chance to drop a wheel. It can take a few taps but they only drop one item each unless you restart the app. In Canterlot, stone pillars and jungle decor yield more wheels per tap.
In the Windows version, two spawn at the start of the game. Gems also spawn after each revival. Pairing this with collected Minecart Wheels from Changelings can make up to 50 per wave of Changelings. After revival, it is sometimes possible to get three gems instead of two. This appears to happen when a already spawned prior to revival, but the player died before getting the , so it remains after revival.
#7 - Daily Login
In older versions, a player was awarded 1 for logging in every 4 days and 2 for logging in every 5 days.
In the current version, gems are earned on specific days played. Refer to the game login chart to look up these days.
Note: On Amazon Underground Actually Free Version, you will get (ranges from 3 to 10 ) every day instead of / 
/the occasional on IOS/Google Play Version but you will still get the decor, the shops, & the ponies.
#8 - Leveling Up
Princess Celestia will reward you with a set number of along with a lot of for reaching each new level in the game. Refer to the chart on that page for the exact number of gems.
#9 - Gift Codes
Gift Codes arrived with update 2.9 (?). Follow this page for additional time limited codes : Gift Code
#10 - Watch Ads
In some game platforms, ads are available to watch when you can click on the button at the top to reach the gem purchasing screen. To the side there will be a green button saying "Get Free Gems". Tap this and you will be taken to view a 10-30 sec advertisement for some other app/game. After the ad is done, return and you will have earned 1 gem.
You can only watch two ads a day, which means 2 a day through this, so make sure you don't forget to watch each day. Those 2 a day can really add up.
However, this changes if you play the game on Android. Here, the button takes you to a list of promotions offered by Tapjoy, usually downloading and using another App, but there are more complex ones as well. Most are free downloads, but some will cost you. Also be mindful of your contract, downloading all those apps could be very costly if you don't use a WLAN connection to do it. There is no daily limit here, but each promotion is one-time and and the offers don't change very often.
(This might not work in the newest version)