there are better pokemon like lapras, walrein, and froslass. Why those pokemon? There stat totals are higher. Lapras= 535 out of 600. Walrein= 530 out of 600. Last but not least, froslass= 480 out of 600. Dewgong is 470.
Power moves for Froslass= Thunder/ blizzard. PM's for lapras= Sheer cold, hydro pump, or thunder.
Power moves for walrein= Sheer cold, blizzard, or earthquake. Power move for dewgong= Sheer cold, that is it.