At the beginning of the game, Delsin Rowe has a very limited array of skills, but he gains access to more of them as the game progresses - this is done in two ways. The first category are the skills which are awarded "automatically", while completing the main story of the game. They are connected with Core Relays found by Delsin (an example Core Relay can be seen on the above screenshot) and "sucking" energy from such a relay awards you with a specific, scripted power.
The second category of skills must be acquired on your own and before you "go shopping", you need to have at least one (or more) Blast Shards (it can be seen on the above screenshot). They can be collected by traveling through the game world and from shot down Tracking Drones - more information can be found in the "Step 8" section.
After acquiring at least one Blast Shard, you can press the Options button, and after that L2 or R2 to get into the screen with character's skill tree. I would recommend to study this tree thoroughly, reading through all the descriptions of each ability. The abilities are divided into three groups. The first are the primary abilities, which unlock a new skill after purchasing them. The second group are the upgrades to already acquired skills - there can be one or more upgrades to a certain skill, depending on the skill type. Each subsequent upgrade improves the ability, by increasing the damage dealt or decreasing the amount of smoke needed, for instance. The third group are the abilities reserved for a good karma (blue ones) or a bad karma (red ones) character. What is more, it may be required to advance to a higher level / type of a hero / villain.
Here's a list of "universal" powers, which should be bought early (the list does not contain the skills unlocked by completing the storyline):
- Drain Smoke - there are five upgrades available, and each one of them increases the amount of smoke supply by 20 percent. Try to unlock at least 1-2 upgrades.
- Double Air Dash - the ability to turn into smoke twice while being airborne is very useful (especially connected with the power to float above the ground), allowing you to reach some of the more distant buildings.
- Cinder Missile - the rockets are extremely useful while dealing with the enemy machines and you should spend those few shards to buy at least one upgrade to this ability.
- Smoke Shot - smoke shots are your primary means of ranged combat, and because of that you should unlock both upgrades to this skill, to lower the cost of using it.
If you are playing a hero (good karma), you should unlock those skills early:
- Vent Healing - this skill is crucial in healing, as it regenerates a fragment of your health bar each time you use a ventilation shaft.
- Sulphur Headshots - it's a useful ability, which comes in handy when you want to disarm and subdue enemies, provided that you have a keen eye and can score headshots frequently.
- Giant Sulphur Bomb - it's a useful Sulphur Bomb upgrade, which will stun a larger group of enemy, reducing the chances of a bomb landing outside its firing range, wasting your precious smoke supply.
If you are playing a villain (bad karma), you should unlock those skills early:
- Enhanced Vent Launch - it's an upgrade to the Vent Dash ability, allowing Delsin to get launched on a greater distance after emerging from a ventilation shaft. You can reach more distant buildings easier thanks to that upgrade.
- Oblitering Blast - it's an enhancement to the Cinder Blast power, which automatically annihilates the attacked enemy and awards you with bar karma points without the need of "manual" finishing off D.U.P. soldiers.
- Dash Slam - this power allows you to immediately execute an enemy, to whom Delsin approached by using a standard "smoke turning".