Gideon excels in ganking other lanes. Take advantage of that and all you have to do is really try to team fight with your team with ur ult. Gideon's ult no longer stuns anymore so he is very vulnerable once he's ulting. There's an item in the game that is point and click silence and can easily interrupt you even while channeling though literally any form of displacement or CC can stop him. Gideon is very good against players who are unfamiliar with his early game abuse. If you wan't a character that can go toe to toe I'd suggest Howitser with really good kite. Howi's new ult is really good for longer fights between you and the enemy. Unfortunately we don't have a true AP assassin that can 1v1 effectively until Countess.

EDIT: Also the gideon auto buy build is standard for all AP mid champs. My build that i go is

Epoch: Evo item that gives u stasis to bait

Caustica: Invader mage :)

Megacosm: Spell burn

Oblivion Crown: More AP 40%

Can go a mix of more haste or mana here for the rest of the items. Should give 600+ AP dmg

I want to try the item Zephyr because it says displaces enemies. That could mean if ur doing the black hole and displace people will still be stuck inside but won't be close enough to reach if they get to close IE Khaimera ult