Predecessor Builds > Lt. Belica > MIDLANE Tech Mage Belica
Couldn't find many other up to meta guides for Midlane Belica. First two items are mandatory as far as this build goes, only swap Combustion for Azure Core if you're getting bursted down early, or your opposing midlane runs down to duo lane and gets a double kill 5 minutes out the gate. After that 3rd and 4th items are interchangeable as needed.
If you're against someone like Countess or an aggressive Khaimera/Crunch jungle, get Spiked Birch after building your first item to help null out their healing potential. Other than that the 5th and 6th items are pretty flexible. In most games Caustica>Oblivion Crown is usually solid, but don't be afraid to grab Overseer if you need more sustain for fights, or Megacosm if you're against a particularly heavy tank team comp. Enjoy :)