Read this steam guide. It does a very good job at introducing a lot of things to the new player to Gemcraft.
Now I’ll add to it some things that they didn’t cover in that guide.
Hot keys. This post alone will probably get Tom to bite if he hasn’t already played this.
See that hotkey for mouse wheel? This is VERY IMPORTANT. You can alter the range of a given tower by hovering over a gem and using the mouse wheel to increase / decrease the range which it will fire (up to the maximum for the gem level). This is critical to get some of the tome chambers opened up as they always have some "kill 400 creeps in this tiny circle) and your towers will invariably be targeting and killing them outside of this circle.
Enraging waves:
Ok, this is a somewhat non-beginner strategy that will open up the game for you in so many ways, it needs to be covered:
Note: Enraging can make it so easy to open up tome locations (kill XXX creep within this circle) as you can gem-bomb an upcoming weaver wave for example 3 or 4 times to generate a lot more creeps to coincide with some other timer like the freeze or curse.
Enraging waves give you both more creeps and tougher creeps. This equates into more mana (mana is generated per kill) and more XP, so you level up faster. Enraging waves is the process of gem-bombing the upcoming waves (the rectangles on the left hand side). To enrage waves the easy way you create a level 1 gem, and you click B or click on the gem-bomb icon. When you click on the gem-bomb icon it shows you this text:
I hate this text, because you only need to read the last sentence. Do it only this way and your life will be so much easier. So, you have your level 1 gem in your inventory, you press B to start bombing, then you press and hold the SHIFT key. This will take that gem you have in your inventory and make a copy of it, and bomb the ground whenever you click. No need to create a bunch of inventory - just have that single gem. This is so important and makes this so easy!
Now, on the upcoming wave diagrams on the left hand side of the screen. Notice when you mouse over them:
When you mouse over, it shows you how many creeps are going to come, how tough they are. When you gem bomb that rectangle, it will turn dark and when you mouse over it, it now shows:
Notice the rage modifiers! By dropping that single gem on the wave, we now have 18 more monsters! Yes they are tougher, but you can earn so much more mana this way.
While there is an science to enraging waves, particularly in WL 1,000 and above, I’m going to ignore that and give you a simple formula:
Enrage waves 3-9 with one gem
Enrage waves 10-19 with two gems
Enrage waves 20-29 with three gems
Enrage waves 30-99 with 4 gems
With these notable exceptions:
+1 for swarmlings
-2 for giants (or fuck giants and never enrage them, seriously they’re hard enough).
With this enraging, you will gain 2x-3x the normal XP you would earn on the field. This will really accelerate your wizard level!
Now, of course, your mileage may vary. As you get above WL 100, you will find that you can enrage more than this. You can also use bigger gems to enrage. But to keep it simple for now, just use this formula and it will help you so much!
You may have to reduce enraging depending upon your battle traits - so YMMV.