The Hwei build for Mid is Horizon Focus, Shadowflame, and Luden's Companion. This LoL Hwei guide for Mid at Platinum+ on 14.3 includes runes, items, skill order, and counters.
Hwei Counters
40.0%
(-5.5%)
40.4%
(-10.2%)
12.3%
(+5.7%)
28.9%
(+10.1%)
775
(-46)