Check out the sources I listed above to get a good understanding of the basics of a reef tank, there is far too much information to disseminate in a single post.I'm confused right now. How should I set up the tank? What kind of corals? Canister filters are too expensive for me. Colin said no starfish, cleaner shrimp are fine and easy.
How should I do everything?
You will get different answers from different people based on their experiences on how to best keep a reef tank. I strongly encourage you to do research beforehand, a reef tank is not similar to a freshwater tank in nearly all facets.
In a nutshell for your questions listed avove:
Stick to a standard method of cured rock, protein skimmer and water changes.
Keep soft corals only.
Yes, avoid seastars but shrimp are fine.