I usually get 2-3 locks in 30m of farming km3 with lepre and luck elixir (I usually just wait until Klaas or Shaz give me one). Or you can do free plat offers and buy luck elixirs (4plat for one). What level are you? Running any tomb is a good way to lvl up or lvl your pets up and if you do km3 you can farm as well as lvl

So don't sell it! Just keep grinding on.