This is my first saltwater tank, its a 29 (i think).
Will a $36, 30gal filter work good or should i get
a better one? How long should I wait to add things
like live rock, coral, and fish.
What kind of beginer fish would be good?
I know, this looks like and is A LOT of reading. However, you need to understand that the keeping of a marine aquarium is not an easy or simple task. You cannot simply rely on your LFS(local fish store) for information - if you do it's likely that you will end up with unhealthy fish or possibly A tank full of dead and dying fish.
A LOT can go wrong with a marine tank and if you do not put enough research into the keeping of one, it's likely that a lot of things will go wrong and you will have no way to correct, becuase of a lack of knowledge.
But to answer your first question, A 30g filter is about half the size you really need, however, mechanicall filtration like you are planning on getting is not recomended as it leads to water quality issues down the line unless you keep a light stocking level (eg., two-three smallish fish in tank your size).
Any other questions should be answered in the links.