Ok I've got all the dragons except for the green and the earth dragon...

Green Dragon:
To get the Green Dragon, go to the marsh in... I think it's home world, but anyway you go to the marsh, go left up to where you see the beeba beeba, if you already have the beeba flute, then he will give you the fruit needed to tame the Wingapede.

Go right to where the other beeba beeba is standing and blow it there, it should take you to Gaia's Navel. Kill about 70% of the monsters there, and a monster should come out in the place you first land. Fight and defeat him, then go up and fight the green dragon.

Yellow Dragon:
Go to Earth Dragon isle, again I don't remember which world (sorry!) but it is the one in which the earth dragon isle doesn't have a hole showing in the middle of it when you take your boat over to the island. Go into the quick sand, down to the bottom and try to push the big animal out of the way. They'll say you can't do it, so go back up and talk to the people on the surface, one of them will say they'll blow it away with explosives, but they need some time. Leave the island and go back, then go down again.

The monster will be gone, talk to the guy standing where the monster blocking the path was, and he'll give you explosives. You can use those to move other monsters into position, etc. That part is pretty simple. If you need more help with that part, ask me and I'll give you more. After you jump in the hole in the middle, go to the right, save you game, and beat him.

Hope this helps!

Okay, ot get the Earth Dragon, you have to go to Earth Dargon Isle (I'm not sure which wolrd, but it's the one where there's no hole in the sand). Go to the lowest level and fall in the quick sand. Explore around a bit until you see a big rock-like monster in the way of a path. Then take the geyser of sand back up to the outside. The Chief explorer will make a comment and clear out the monster (rock roach). After that, you are allowed to enter the room. You'll see three active geysers and one dormant. Using dynamite given to you, defeat each Rock Roach and blow them up. They'll land on the three small ones and activate the large one. Jump into it to go to the Earth Dragon.
To get the green Dragon, you have to pay a visit to the Beebas of Hydra Marsh (Another world, I believe). If you already have the Beeba Flute, they'll give you fruit. If not, they'll give you the flute and you'll have to go to the other world for the fruit. Go to the very top of the Marsh and play the Flute. You'll summon a Wingapede which will give you a ride to Gaea's Navel. Whwn you get there, you'll get another character and a tedious task. You have to destroy ALL the monsters on the island. After you do that, you'll be attacked by a boss monster (he's not that hard). After you defeat him, you can go kill the Green Dragon. Watch out though, he uses Carnivore a lot (it inflicts serious damage an poison. A Carnivore trap would be helpful).

This question is big but there is no problem.
Now if you want to get the green dragon go to hydra marshes and go to the place where you got the Beeba Flute and a beeba thing will fight you and if you win he will give you an ancient fruit go to the next screen north and you will find another beeba standing go beside him and use the beeba flue to go to the Gaea's Navel.Fight and kill all monsters and the barrier to green dragon will vanish.
To get the earth dragon go to the earth dragon isle and keep going down to where a monster was blocking the path it is now gone and you will be told that you should get the sand boil to function so go and push the monsters to the halls after fighting and killing them all.A monster will remain standing in it's place.Go out of the screen and talk to the first explorer you see and he will give you an explosive.Use it on the monster and the sand boil will begin functioning and you should jump in it to go to the earth dragon.

Hope I Helped.
Good Luck.