The Katarina build for Mid is Lich Bane, Zhonya's Hourglass, and Shadowflame. This LoL Katarina guide for Mid at Platinum+ on 14.3 includes runes, items, skill order, and counters.
Katarina Counters
50.6%
(-1.3%)
43.6%
(-1.9%)
6.0%
(+0.2%)
7.2%
(+1.2%)
878
(-2)