if you take out suicune get a lapras. it is a god
Umbreon and Suicun are good defensive pokemon
To replace Suicun, Tentacruel is really good
and to replace Umbreon... maybe Gengar?
if you really want a grass type, Celebi and Sceptile are good
Get a tyranitar
hmmm ... well you could maybe add a porygon 2 or houndoom those to pokemon i know are great , if your looking for a deffence pokemon then i would have donphan and skarmory
u shud add a togetic.
to get giratina you needed to get the arceus event and made arceus create giratina lvl1 and to get venasaur you need to beat red he's on top of mount silver and he has the highest level pokemon of any game when you beat him go to prof oak and he'll give you the choice or bulbasaur squirtle or charmander also when you beat red you can go to silph co. in saffron city and steven will be in there and gives you a choice of a green gem a red gem or a blue gem which represent torchic(red) mudkip(blue) and treeko (green) i'd recommend replacing umbreon with giratina but if you replace suicune to replace it with a water starter so ou don't have that big hole you don't really need a grass type they're not all too great cuz most people's favourite type is fire and that'd kill a grass type and grass is mainly only good againt ground rock and water but a water pokemon could take on ground rock and fire while you could use ampharos for water types hope this helps sorry for long answer
After you defeat Red, Professor Oak will give you one.
get a jarachi 3:0