Well, the earliest you can get a grass type in Gold version is to pick Chikorita, but I'm guessing you didn't. The first Grass- type in the wild on Gold is Bellsprout on Route 31. It starts at level 3, however, so it'll take quite a lot of training to get it to a reasonable level.
you find them roaming in the grass
near safari zone were the grass is
just run in the grass
the grass behind the daycare. You will find him in there keep searching for it.
Furret. Just evolve a sentret.
go to the 8th in johto and go to the route to the bottom of the town and near the cave, in the patch of grass, you can find them.
you can find a ditto in the grass outside canalve city. if you want to get a ditto you must have the pokeradar and the natinol dex. also defeated the elite 4. first you go to the grass then you use the pokeradar and when the grass shakes where there is a Pokemon look for gold on it. it is usually a ditto.
potatoes
Grass blocks in pokemon heart gold are were wild pokemon hide you may catch them and train them or you may beat them with your pokemon and earn exp.
You can find Pokemon in grass, caves, fishing or surfing.
In the grass...
Mr. Pokemon lives on Route 30 in Pokemon Gold. His house is in the northeastern part of the Route after a few patches of grass.