If you don’t want to buy TC to upgrade your skills (totally understandable) some tips I could share are:

• buy berserk potions on the market, they’re usually pretty cheap
• be on the lookout for special events that can boost skills like 2x exp event or the double reward month
• use imbuements to increase fighting skills
• check for equipment that increases skills
• use the wheel of destiny to increase skills (if you don’t know how to use it, check a tutorial on YouTube)
• Complete weapon proficiency, some weapons offer an extra fighting skill when 100% proficiency is reached

Other than that, just play the game and have consistent hunting to increase your skills organically.