So since there are so many "this game is hard posts" heres some useful starting out tips to get you started into the game.
Useful Starting Out Tips
Dual Gems are more Powerful then Pure Gems when in towers. They get an inherent damage increase at the cost of the specials.
Learn to modify the targeting priority. A few simple changes is all it takes to make a hard level into an easy level. Don't be afraid to use Random or Highest Armor or Lowest Hitpoints and having a mix of them throughout the maze. I personally use random a lot on my front line gems to soften up a bunch of the enemies. More so when you have armor or poison gems on to spread it around. Nearest to Orb is not always the best option.
Don't spend all of your skill points. More often then not, having the extra mana at the start will outweigh the skill increase since you can have higher starting gem grades and can anger a lot more waves.
Don't be afraid to move gems around the towers when needed. A gem at the front line doing nothing when the monsters are near a back tower with no gems seems like a good place to put that gem temporarly.
Do all the nodes as much as you can. Each node had 3 XP values, Journey, Endurance and Trial and all 3 have seperate XP values. The first pass thru each node gives full xp gained while future passes give the XP difference from your prior best to your new best.
Early on, More Gems are better then higher grade gems. 4 gems do more damage then if all 4 were combined (2 grades higher).
When you having hard time with alot of swarms just use Poison trap and set priority to swarm it help alot.