This is a very crucial section that every beginner should read and understand. First of all, your damage sources come from Boons and Daedalus Hammers. Secondly, you should always focus on building your damage in one source of damage rather than spreading them across 3 sources.

The 3 sources of damage are "Attack", "Special", and "Cast". You'll see these when you pick up a Boon.

For example, you use Twin Fists for your run, then you have Artemis as your very first Boon and she gives you 3 options:

• Deadly Strike: Your Attack is stronger, with +15% chance to deal Critical damage, Attack damage +20%.
• Deadly Flourish: Your Special is stronger, with +20% chance to deal Critical Damage, Special damage +40%.
• Hunter's Flare: Your Cast damages foes around you, with a 10% Critical chance, Cast damage 80.

As you can see in the descriptions above that you have an option to either improve your "Attack", "Special", or "Cast". In case, you decide to choose "Deadly Flourish" which improves your "Special" damage, you should always focus on increasing your Special damage when picking up next Boons/Daedalus Hammers.

Later on, you pick up a Daedalus Hammer which gives the following options:

• Long Knuckle: Your Attack has more range and deals +10% damage.
• Heavy Knuckle: Your Attack becomes a slower 3-hit sequence, each deals 40 base damage.
• Flying Cutter: Hold Special for longer range and up to +100% base damage.

Now, since your Special is already improved and has higher damage by Artemis's Boon, your best option here is to choose Flying Cutter which further amplify your Special damage more up to 100%. Sometimes, the options provided don't always give you what you want so you'll have to use your best judgement for that specific circumstance. 

Call is the 4th source of damage you can build as a secondary. it consumes God Gauge so you cannot always use it. The God Gauge increases when you hit or get hit by the enemies during an encounter. The God Gauge will be empty after you clear an encounter.

When you start your run, you will always receive your first Boon at the entrance of Tartarus. This is a very special Boon because:

1. the choices provided by the Boon will not change even you "Give Up" the escape attempt. The only way to reset the options is to let Zagreus die.
2. you can force to receive the boon from a specific god by equip the Keepsakes from that god. For example, if you want your first boon to be from Zeus, you have to equip "Thunder Signet".

With this information, you can always try a run and see what are the option available from the first Boon, then "Give Up" the run and choose a weapon and keepsakes to match whatever source of damage provided to you.