"*I made it*", would generally be used when describing something you have done i.e.:

> Who made this cake?
> 
> "I made it"

You would say, "*I've made it*" while talking about being accepted into something, because:

> I've

is just:

> I have 

Shrunk down so you would say something like:

> Who made the basketball team?

> I've made the basketball team!