More detailed instructions for dumb people like me:
Think of your hearts as energy to spend, and not a health gauge. Spend as much of it as possible before levelling up or using a heal-scroll.
One of the spaces next to the dragon has an egg (power 0, exp 3).
Check what directions the Minotaurs (power of 6) are facing when revealed:
Minotaurs are always facing away from treasure, one of the three squares behind them contains a treasure chest.
Gazers (power 5) obscure the squares around them up to 2 orthogonal spaces away (1 diagonal); those squares will show as ? until you kill the gazer. Revealing a couple of ? squares should let you guess where the gazer is hiding.
The slash you see when destroying a gazer is not the gazer destroying enemies around it, just the obscuring effect wearing off.
If you figure out a square is an 11, that's a mimic, they don't drop anything special when killed so by the time you're strong enough to fight them, it might not be worth it unless you're trying to clear the whole board.
Romeo and Juliet (power 9 each) always drop a healing scroll when defeated.
When you have 10 hearts you can fight the mine master, hiding in one of the corners, beating them will reveal a mine-defusing scroll which, when collected, will defuse all mines on the board, letting you collect them as treasure.
Don't forget to pick up the mine-defusing scroll before picking up mines.
The blue cat (power 5) will drop a "reveal rats" scroll when defeated. useful when you just need to spend 1 heart
The crystal ball scroll can be useless if it reveals a spot near a corner, edge, or an area you've mostly uncovered by yourself. Don't rely on it to save a bad run.
If you see multiples of 8, there's probably a slime wizard nearby. That guy is surrounded by purple slimes with a power of 8 each. The slime wizard has a power of 1 and drops a scroll of detect slimes, so if you know where the power 8 purple slimes are, you can jump over them to attack the slime wizard directly (power of 1).
The game will not stop you from clicking a heal scroll if your health is full, so don't double-click treasure chests expecting exp unless you know you need to waste it to reveal the number underneath.