It took me 11 months to get a shiny karp. 98.000 solo encounters.
It took me 1428 eggs to get charizard.. it is just random, if you really want a shiny go hunt it and stick to it till u get it!
Hi welcome to Pokemmo,
it took me 11 months , 98.163 solo encounters to get shiny karp, I hope you are more lucky than I am ^^
Now that karp is in hordes it could be an easy hunt, just stay focussed on the shiny and don't give in!
enjoy the game