Sin Mark is quite an easy game. But it does take time (and you might get bored of it before you finish it). These are the easy steps to winning Sin Mark.
1. Make sure you have enough room before collecting runes. 2. Always collect runes. 3. Make the Arrow Storm and Frezze as soon as possible. (This will help you A LOT later.) 4. Make sure you have enough mana for Arrow Storm and you have enough room for the arrows to split to destroy the Gates. 5. Do this 3 times on each level. 6. If an enemy is too close to kill before it attacks you, use Frezze (this will frezze them for about 10 seconds) and use normal arrows rapidly to kill or nearly kill them. 7. Make any other high-level spells as soon as possible 8. Once you have made it to the last level (with the dragon), go to the left end of the map until you can'go any further. 9. It looks like as if the dragon is going to kill you, but actually it can't reach you (glitch). So use Arrow Storm or whatever else you have to kill the dragon!