I'm not going to comment on how to build combos and such, as that is all subject to how people like to build. But, I will be adding a couple links and some good information.
Gems
Gems are when you form blocks of 2x2 or higher, and they "morph" in to one solid big block; a gem. When break gems, they send swords to your opponent. When building a break, never build more than 3 gems in your combo. If you build 4 gems, and send them all in one combo, the 4th gem would get wasted as you can only send 3 swords per break, as swords can't stack onto one another.
Sprinkles
Sprinkles are single blocks that are not morphed into gems. Sprinkles send sprinkles to your opponent, and the amount of sprinkles you send is simple. For a single break of 3 single blocks, you would send your enemy 3 sprinkles. But say you tripled a sprinkles combo of say, 6 blocks (Breakers count as sprinkles) your opponent would receive 18v sprinkles.
If Y equals to the amount of blocks (sprinkles) you send, and X equals to the size of the combo (Single=1, Double=2, Triple=3, Bingo-4 etc) the formula is S=Y*X. S for sprinkles.
Extra Tips
A little extra tip is to always build your combo in columns 3-4, as the only way for the person to screw up your combo is to sprinkle you, or do a 3 gems break on you (If they had enough time to build that before you could send off your break, you did something wrong). This is because when someone sends gems at you, the first sword lands in column 1-2, the second in 5-6 and the third in column 3-4, hence why all instas require you to make a triple (Bunny-toothing and 3x3 combos require you to build a triple+ as well, but that is because the swords wouldn't be big enough otherwise, not because of lack of gems).
Hope some of that helped, but if you want to learn more on drop patterns and where pieces land, read this: http://yppedia.puzzlepirates.com/Black_Death_Sword_and_Sprinkle_Placement_Guide
- Kadazzle