Try to keep ur CP as low as possible, as it affects how strong u are vs the mob "statistically only". Ur equip is define how OP u r, skills just amplify it. If u have higher CP than the mob, it becomes weak/-est, and both ur exp reward and loot table will be screwed.
What affect CP is ur HP/MP, Stats{Str/Dex/Wil/Luk}(from lvlup, skill, aging) and Skills. However, Stats from Title/Item do not factor in the CP formula.
Do not easily rank up ur skill unless its mandatory. If ur CP is too high for ur equipment, u r gonna have bad time.