Voltar I usually start off with 125 solar and go for turn healing wave into solar and then buy the orb.
Once i get enough cash then buy the healing bot and focus on either upgrading healing amount of orb damage, speed, attack power. Once the orbs are fully upgraded then i work on the heal wave damage and range. When your a high enough level you can have 2 healing damage increase waves.
Do not use convert healing wave into damage though since its weak for what it really utalizes.
Tips: you play great with clunk and yuri on the team and leon. Also the new dlc tank guy is great for protection and healing.
Heal leons clones especially if they can attack as their act just like bots. Drop your healing becon near the crowd and mash the orbs and your heal wave.
You may not get tons of kills at first but near the end you might get more wins.
clunk build focus on vacuum bite and increase max health. Then increase bite damage. Increase your overall health as much as you can and then buy missle upgrades for speed and damage if you want turret and bot kills or go for suicide and slow aura.
Honestly in the right hands clunk is a beast especially with voltar healing him.
Counter builds: anything which shoots through the wave of enemies and healing power. Bullets that pass through mutliple characters.
Derpl: Get the solar generator and the turret and then the nuke and then save up for the 21% shield. Then take turns getting a health up grade, the other shield upgrade and so on then finish that up with the health regenerator. Boost up the power of the nuke and you're gold.
Froggy: Solar generator, speed boost, splash dash, stun increase, cool down - 1.2 then twister, twister shield, twister tweezers, twister duration increase. Throw in some health ups if necessary.
All your children are poor unfortunate victims of systems beyond their control, a plague upon your ignorance and the gray despair of your ugly life.