Diamonds are one of the currencies in the game.
Diamonds are frequently offered (in small amounts) as rewards for Quests, Achievements, Events, etc. The fact that Diamonds are given for in-game activities is a big reason that playing as a Free-To-Play player is a viable option.
However, in terms of time required, the most efficient way to acquire diamonds is via recharging (purchasing for real world money).
You aren't FORCED to spend diamonds at any point in the game. However doing so will often allow you to acquire Heroes, Angels, and Items faster than you can without them. As in most Free-To-Play games, the top tier players all spend money on diamonds.
Some tips and tricks for acquiring / spending diamonds...
Acquiring for Free Edit
Completing the Elite (Hard) versions of the various Adventure Stages will reward you with an Achievement which will provide diamonds as part of it's reward. Also a few Events like the Daily "Complete 14 Quests", will offer a few diamonds as rewards.
If you are willing to spend some money on Diamonds, there are a few tips to optimize your purchasing power.
- The monthly option is the best "value for your money".
- For a fairly low cost, you receive 200 diamonds every day for 30 days.
- You MUST login each day and claim them from your Quests log.
- GT Arcade frequently (always?) offers bonuses for recharging on the weekends
Some tips on spending your Diamonds:
- Top players tend to spend diamonds on upgrading their Training Slots so their heroes / angels will level up faster
- Spending 500 diamonds per day to purchase Stamina
- Spending diamonds on Gold can be a good buy if you have some to spare
- Spending a few diamonds (250 or so) opening Angel Trial chests can help you accomplish Event goals
- Spending on Super Divination might be a good idea, if...
- Sometimes buying just one Super Divination will complete several Event goals
- If you have 4999 Diamonds, the 10-times Super Divination is a good deal for many reasons
- It's a savings off 10 individual Super Divinations
- Spending that much (especially on weekends when Spend style Events are common) will trigger a lot of event rewards
- Significantly: There is typically an Event which will basically "refund" half (2500) of those diamonds back to you for completing 10 Super Divination draws