Advice for 3 feet tank

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Finally, I have decided to convert my 3 feet tank into marine tank. I want to start from the begining, with something simple & low cost.

This is what I currently have :-
1. Tank size : 50 cm (height) x 100 cm x 45 cm (its not mistaken its a standard 3 feet tank)
2. I m using Jebo cannister previously for my fresh water tank, model 835
3. Without any lighting at the moment, with temp of 27'c

Anyone can help me out on step by step. Like
1. What kind of salt I need, how much?
2. Hydrometer?
3. How many coral sand I need?
4. Live rock?
5. Lighthing?

Can I re-used my exisiting filter? Do I need to do upgrade on the filter media?

I want to start up with some simple and easy to keep fish.