You’ll find yourself in a rocky area. Follow the path down. At the gap, choose to either jump down or turn back. Get the Mystile in the chest on the right and the green Elixer to your left. Keep going along the path. The chest in the north has a Speed Source in it. There is a Tetra Elemental in the chest between the broken structures.
On the main path, head east then north. At the path split go west and get the Megalixer from the chest and retrack to the path split and go north. The chest on the right has another Megalixer in it. Keep going north to the bridge and work your way down it to the Place of Gathering.
At the start of this path, whoever else (apart from your current party)you told to go on the left path will ask whether to take the upper or lower path. Take the path you didn’t tell the others to go.
Jump down to the brown branch thing and go to the right and press up to get to another branch. Then go right and get the Magic Source from the chest and go back to the first branch. Go left then north to the edge. Here Cloud will jump to the rocks. Go north along the path and Cloud will dive into the water and re surface on the other side. Get the Remedy from the chest by going left then north. Make your way right and take the upper path to get to a new screen. Go to the far right and pick up a Hero Drink from the chest. Take the upper route and go all the way left and to the north to get to a chest with a Vaccine in. Walk in front of the rock on the right and take the path up to the top and pick up the Shield materia there. From here walk to the left and press down to climb down. Cloud will get his feet wet again and re surface near a chest, this time with an Imperial Guard in. After getting it, press down to make Cloud re enter the water and go back to the other side of the screen.
Run south then east to arrive in a new area. This place can be annoying due to layout and there isn’t a clear path, but go to the left and work your way down. Go towards the centre of the screen and then north to end up near a small dot. Press O to get the W-Magic materia. Now make your way to the light by going south then east. When you get to the light, examine the bit of darkness to get a Counter materia. The go west then north to get to the Place of Gathering.
Jump down the columns and get the Remedy from the chest. Go right and go up the steps to get to an Elixer in a chest. Make your way back to the first chest and jump down to the column at the bottom of the ledge to get an X-Potion in a chest. Go southeast to the next screen. Jump down and go left to get a Turbo Ether. Follow the path and get the Vaccine from the chest. Go west then south and jump across some more columns. Go to the south and then right to get down to a ledge with another X Potion. Go to the left over the bridge and drop down. Keep going right and then down the steps. There is a chest to the left with a Turbo Ether inside. Go to the left and there is a materia floating in the air. You will jump onto that platform but you need to press O at the right time (or just hammer it) to pick up the materia before jumping onto the western ledge. It’s the Mega-All materia and you can only get it while jumping from the south not from the western ledge.
Anyway, get the Speed Source from the chest on the western ledge and make your way south to the Place of Gathering.