Aerith's limit breaks are all healing techniques.
Healing Wind
Aerith casts wind on your allies, healing some lost HP
Seal Evil
Stops and contrains enemies's attacks for a short period of time
Breath of the Earth
Aerith cures all abnormal status caused upon your team
Fury Brand
Aerith allows your other allies's limit break gauges to fill to the max, except her own
Planet Protector
Aerith causes the status peerless, making your team invincible for a short period of time.
Pulse of Life
Aerith fully restores all lost HP and MP, and reviving all fallen members
Great Gospel
Aerith restores all lost HP and MP, and makes your party invincible for a short period of time, depending on your ATB
Once Dio gives you the buggy, head towards Costal del Sol. DO NOT GET OUT OF THE BUGGY, DRIVE THROUGH THE TOWN, and head on the Cargo Ship. You'll be back at the Junon docks. You'll find a guy in a sailor suit waving his arms. Talk to him, and tell him that you want to get out of town on a helicopter. After you do that, you'll be outside with your buggy. If you got Yuffie around Junon, then you should know where the forests are. On the right side of the big forest, next to the mountain, head across the shallow river, and in the cave that's there. Talk to the guy inside, and if you've fought the right amount of battles, he should give you a Mythril. Sometimes he'll give you something else, or he'll tell you how many times you've fought, escaped, and something about Materia. If you didn't get the Mythril, head outside and fight a battle. You must match up the number of times you've fought with the old man's numbers. So check everytime after you've fought a battle. When you get the Mythril, head back where you came from, and proceed with rest of the game. Once you meet Cid, and have the Tiny Bronco, head to the house that's near Gongaga village. The weapons shop owner will talk to you for a while, then select to change the subject. He'll ask if you have a Mythril. Give it to him. He'll then allow you to open up a small box, or a big box. You only have ONE choice, so don't waste your time...choose the SMALL BOX on the second floor. Inside is Great Gospel!