Ok, I searched around in the forums a lot and found nothing really useful.. until I read that I should make a Yellow/Orange/Lime Combo Gem.
I messed around with it and at around level 400, I have been able to beat the endurance without any issues and fairly quick!
Here’s what I have (Premium only, never tried it without premium.. sorry)
All (except for Waves getting harder) gives a multiplier of 45.45 with Shadow
Traps, Amplifier, Triple Gem Mastery, Readiness, Chain Hit Mastery, Multiple Damage Mastery, Flexiblity, Wild Gem, Recharge, Radiance
Split the rest between Replenish > Focus > Resonance.
Setup one tower in a location with possibility of 8 amps in future.
Start with 1Tower and 3-4 Amps.
Depending on map and your skills:
You should create a grade 6 Yellow, grade 5 Lime and Grade 5 Orange. Combine them to get a grade 7 triple gem.
Create a grade 5 Yellow and grade 4 lime and orange and combine for a grade 6 gem.
Now I create a grade 2 y, grade 1 lime and orange and combine to form a grade 3. Duplicate it 2-3 times for each of your amp.
Once that is done. Look at your Gem’s total damage (I assume it to be (min+max)/2 * Multiple Damage multiplier)
Now, my goal is to generate waves with 5-6 times the HP of my Gem (after wave 20, I even go upto 10-15 times the HP)
I keep doing that and once I get my Gem to level 9 and Amp gems to level 6 (adding amps until there are all 8) .. I focus on getting mana pool upgrades until my multiplier becomes 2.5
Around level 25-30 I Make a trap close to the starting point with 6 Amps. And move the setup of Tower to the trap.
This should instantly double your mana income.. Keep on upgrading the gem to level 12-13, and if monsters slip out (then quickly create 10tower, 8amp setup) (use the old one) and kill the monsters which slipped out.
Around level 35.. make 3-4 Shrines to help in case monsters become too strong.. but I never have to use Shrines.
Once the main trap gem is level 15.. I start to shift the focus on Mana gain, and my next few upgrades are with higher Mana gain.
You are Done
Keep upgrading the gem till you have a trap = 21, amps = 17 setup done.
Once that is done.. stop Summoning and just ctrl+click to summon all waves.. you shouldn’t have to do anything more. I usually reach that around level 100.
I usually mass duplicate gems and then combine them to upgrade, because it takes too much mana to upgrade mana
pool after around 1M mana.
Focus now on getting ALL the Amulets you can.
I hope it helps other newbies!