Afraid of Top?
Don't be. The top lane may be brutal punishment, but pick Galio and you are save. With his legendary Bulwark-shield and two potent Aoe CC abilities he ist unkillable disruption machine that can get away where others are long dead. His passive Runic Skin and high base damages make defensive items a natural choice giving you even more room for errors. With Righteous Gust he can get to squishy targets and stays relevant even with minimal farm. Enemies will pay if they ignore him.

Runes
Galio isn't particularly rune-dependent, any standard set will do. MR runes are especially good, MPen helps but is not essential, CDR can give the edge with his long cooldowns.

Masteries
I like the heal, I think it pays of. Galio is not the choice if you want to 1v1 someone, his burst lacks and his trades consume too much mana. He needs an ally to kill, but then its pretty save even without offensive masteries. People ignore how strong his shield is, the only really big heal that was left untouched by patches and reworks, but got acctually buffed with increased healing options. So I would advise all the lane sustain you can get. Farm and hold the fort!

Skills
Bulwark first! It turns dives around, decides trades in your favor, and makes minion heal you to full. And, thanks to your passive, even gives damage. Delay Righteous Gust until you need the speed, its not worth for damage early. Remember you can shield while in Idol of Durand and its the perfect setup for a Resolute Smite - after finishing it, casting will end your ult!.

Items
His laneing is facilitated with Catalyst of Aeons. This also builds into a wonderful teamfight item for later: Turbo Chemtank. Very good synergy for damage has Abyssal Mask. Spirit Visage is a great boost to any heals you get, but a bit overkill in lane. Zz'Rot Portal is by far the better lane option. It frees you for roams and provides you with the tower pressure you lack. Anyone too lazy to farm has found a friend with this. With speed-modifiers from Turbo Chemtank, Raptor Cloak, Righteous Gust and maybe Dead Man's Plate you might even skip boots or stay with Boots.

How does it work?
Learn to Rightheous- -Rightehous Gust like a maniak into 5 enemies. Don't ult right away! Time your shield to tank most of the damage after (!) you lost some health. Slow high priority targets and give them all you have. If the enemy wastes valuable time and skills to deal with you, while you survive and you manage to severly cripple or even kill enemy carries, you did your job right. Remember that because you are in the the midst of their team, debuff items you carry have lasting effects - if you stay alife.

End
Thanks for reading. Credits to the awesome MobaFire community!