Gall - Only advice i can give is SPAM SPAM SPAM as Gall. Don't be scared to keep spamming your non-heroic abilities for any and all reasons. Gall has low cool down and good poke with his abilities with no mana usage. This makes him a monster to deal with in lane.

I wouldn't recommend going Support Gall. I like getting the Dread Shield (The sustain you get if you even hit 2 enemies is worth it) at level 13 but that's about it. You CAN go support and it is viable but it seems like a waste with all the damage Gall can dish out.

Cho - As Cho, a lot of what you do is going to be based on how good your Gall is. The Gall is where most of the damage is going to come from. You hit hard too of course but a good Gall will always out damage you and most of the team. IMO Gall should build towards tanky/sustain and let Gall focus on dmg in most games.

If you guys have good teamwork and a solid team, going CC Gall is beastly. So many slows and body blocking so your team can deal the ultimate damage. But your team has to be with you harassing them so they won't turn around and blow you up.