Steam has a few guides. "Learning Skill and Level CAP" by Bladewind should be enough to help you get started.
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For more info on skills, I've arranged the Passive Skills by type and added a description. The skills should stack up (like the HG Mastery 10% per level) or gradually increase in increments (like the Regen of Maiden by 15 HP per level) until you reach the max LVL 10. But a few skills like Soft Skin of Maiden will max out at LVL 3 or Scavenger at LVL 5.
*I didn't include Active Skills, H Skills or Carrying Capacity.
EQUIPMENT
HG Mastery - Damage dealt by Pistol +10%.
SG Mastery - Damage dealt by Shotgun +10%.
AR Mastery - Damage dealt by Assault Rifle +10%.
GL Mastery - Damage dealt by Grenade Launcher +10%.
Hand Grenade Mastery - Damage dealt by Hand Grenade +20%.
Dagger Mastery - Damage dealt by Dagger +20%.
Flashbang Mastery - Flashbang reduces enemy AGI by 6%, prolonging stun time.
Scavenger - 40% chance of ammo drops after battle.
HP
Health - HP MAX +50.
Regen - 20% chance to heal 15/30/45/etc. HP when hit by enemy.
Fortitude - Every step forward has a 50% chance to restore 10/20/30/etc. HP.
Prayer - Auto revive once per exploration. Upon revival, HP +5%/+10%/+15%/etc., VP -5/-10/-15/etc.
SP
Will - SP MAX +5.
Pain - 50% chance to recover 1/2/3/etc. SP when hit by enemy.
Spirit - 50% chance to restore 2/4/6/etc. SP on each step forward.
Zeal - 50% chance of recovering 5/10/15/etc. SP after battle.
Calmness - While under the effect of Sedative, recover 5/10/15/etc. SP on each step forward.
ATK
Shot - Damage dealt by firearms +5%.
CQC - Damage dealt by Kick and Dagger +10%.
Endurance - Damage taken -3%.
Breath - 50% chance of getting a ATK+20%/+40%/+60%/etc. bonus for 1 turn after Breathe.
Tactics - When switching weapons in battle, ATK +10%/+20%/+30%/etc. for 1 turn.
Tenderness - 50% chance to debuff enemy team's ATK by 10%/20%/30%/etc. for 3 turns at start of battle.
Thorn - 50% chance to reflect 20/40/60/etc. damage when hit by enemy.
Rage - When your HP is lower than 50%, ATK+20%/+40%/+60%/etc.
Crisis - When your HP is lower than 50%, damage taken -5%/-10%/-15%/etc.
CRI
Resolute - Critical Damage +10%.
Acumen - Critical Rate +5%.
Soft - Chance of being Critically Hit -30%.
AGI
Speed - AGI +2.
Surge - When your HP is lower than 50%, AGI+10%/+20%/+30%/etc.
Splendor - 50% chance to get AGI +20%/+40%/+60%/etc. bonus for 2 turns at start of battle.
Dexterity - AGI +30%/+60%/+90%/etc. for 1 turn after reloading in battle.
Ingenuity - AGI +10%/+20%/+30%/etc. for 3 turns after using items in battle.
Charge - Get a AGI +20%/+40%/+60%/etc. bonus for 5 turns after throwing item in battle.
Carnival - When there are burning enemies in battle, AGI+10/+20/+30/etc.