Soooooo, time to copy the stuff to here! A truly Heroic guide begins!
Time to start with the Classes!
So, assuming you have all the gods, let's start with the Adventurer. The Adventurer focuses on speed, and buffing itself with an AGI buff with a relatively short cooldown. Its other ability makes consecutive attacks (Referring to both auto-attacks and abilities,) deal more damage. So, the best way to capitalize on that is quick auto-attacks and similarly quick abilities, both represented by Hermes and Poseidon respectively. Hermes gives a huge AGI buff, perfect for the Adventurer, as well as allowing several auto-attacks to happen at once with Special Delivery. Hermes's passive reduces cooldowns by a flat amount after each auto-attack, made even better with the aforementioned Special Delivery. Hermes also gives an AGI/ATK buffing ability, and auto-attack reduction if you have him equipped. Poseidon is much of the same boat, giving an AGI bonus if you have him equipped. All his abilities just deal damage, but are more effective if the prior ability was a Poseidon ability. His passive makes water damaging abilities used immediately after other water damaging abilities get an immediate cooldown reduction. So, now that the basics are down, we'll talk about how these work together. Hermes makes Poseidon's abilities trigger more, and if you have the Liquid Saber or Poseidons Trident, all abilities get a cooldown reduction, since Hermes and Adventurers abilities are elementless, and thus are changed to water abilities. All of which is boosted by Thousand Cuts, making this quick barrage of attacks more and more powerful after each attack. I recommend the Poseidon set for equipment, giving extra water damage, ability and auto-attack cooldown reduction, and the 5 set bonus giving each water ability (ie. all your damaging abilities) a 10% chance to activate twice. For gems, I recommend opals for damage, or topaz's to deal with their low health pool. The Adventurer works best with Monk/Priest using Apollo/Hermes, in which case replace Hermes on the adventurer with Artemis, and add rubies instead of topazes.
Next! The Archer! Best way to describe them: Debuffs and crits! The passive ability makes enemies with a status effect applied by the Archer take extra damage. Their abilities, understandably, apply a DOT effect, and stun the enemy. For gods, the first tip is never remove Artemis from the Archer. They complement each other perfectly. Artemis increases crit chance and damage on debuffed enemies, and two of her abilities debuff the enemy, while the third is insanely powerful damage-wise, and increases debuff duration for all debuffs on the attacked enemy. The next god is Ares, another obvious choice. All his abilities apply DOT effects, which are counted as negative status effects/debuffs. His passive increases DOT effectiveness per DOT, synergizing with Archer's ability. Recommended gems are rubies or opals, and the Ares set is recommended due to the 5 set ability allowing DOT's to critically hit. Archer pairs well with the Priest/Monk using Dionysus & Hermes, instead of what they would normally use.