Notes before starting - Wyverns follow the black arrows to attack the outside crystal. 1. That etherial spike trap is just there to keep spiders off the northeast camp. May not be required, but I like to use up units and it fit the need. 2. That second harpoon turret is not buffed. Again, just filling units but this helps thin the wyverns in later waves if hosting for a 4 man group.
Initial build - Drop all 10 auras and 3-4 archers in their lines until out of mana. Care for the wyverns coming from the north. If your auras / minions don't have the range to stop them at the first wave, build one or two of your archers by the outside crystal then move them to a line once the first wave is over.
Second Wave Build - You should have enough mana to finish the build from here. Add a buff beam to each camp, add the harpoon turrets barely touching the beam to get buffed, add the traps (just filling units), then finally add the rest of the minions. If your harpoon turrets aren't buffed, move the units away then buff the harpoons then move the minions onto the line.
Upgrade order - Buff beams -> Auras -> Harpoons -> Everything else
Final notes: I have been using this build since my builders reached the low 2k mark. You can replace the harpoons with any other AoE tower of your choice if that is your thing. The mage minions by the north camps is there for lower stat builders. The orcs start gaining enough hp to tank the auras and start attacking the line around wave 30. A higher stat summoner could replace those with more archers, but the aoe the mage attacks with is still healpful. Once everything is 3 star, remember to heal between waves. Pure strat does not allow for healing during waves. One of the best EXP farms in the game.