In early game, i can recommend to spot their jungle as often as possible to fall behind in level a lot. Then recall for confusing them and mindgame like a baws. Your skillshots don't have to land, cause you play an AD oriented Karma (ofc).
In Midgame go for some crit and attack speed. try to focus tanks (jungler, toplane, some supports). NEVER focus the adc cause he will have lifesteal. This Karma build has a ridiculous lategame with dat solobaron build. Also avoid teamfights. YOU MIGHT DIE!!!
That was a short Karma build. I hope you enjoyed it much and now go win ur games.
Your RiverDota

Build some Armor Pen marks, Movement Speed Quints, Scaling magic resist Glyphs and Seals of scaling Health