How to Actuallly Get Stronger
Mediating to increase Levels is the worst way to get stronger.
Your damage is affected by your Combat stat. If you never spar/duel with anyone, you will do -50% damage and take +50% more damage at the lowest Combat.
Each point of Str, Con, and Int also provide bonuses to ATK/DEF based on your current Level. Pumping those up will give you more power than just Leveling up with Low Stats.
For example: Level 100 with 10 Str will have 1500 Atk while a Level 100 with 1 Str will have 150 Atk.