First up, never set up a marine tank when the word "urgent" is involved unless it's a hospital tank or something and the time-sensitive part is to do with salvaging an existing marine system that is in trouble. If you are in a situation where you either have to act super fast to have a marine tank or lose the opportunity, then frankly you should pass and wait until you are in a position to do things slowly and calmly. Slow and steady is what it takes in marine.
gouramiKeeper said:
Whats my VERY CHEAPEST option since im slowly running out of money.
Marine tanks generally have elevated maintenance costs. If you are not financially stable, it is not a good thing to start. You can do marine tanks super cheap on ramen-noodles type budgets (I have done it), but you will be looking at a pretty limited selection of stock and you have to be VERY CAREFUL. When I was financially strained, all I kept were hermit crabs and a few snails. Keeping hardy, invert-only tanks that most people would consider boring (obviously I don't think it's boring, but many do) is really the only way to do a small tank safely and easily for cheap.
If you are committed to starting up a tank right now, you can save money by being patient. Buy LR slowly as you have a bit of money spare here and there, and buy dry rock to make up part of the mass you'll need and wait for it to cure. Going that rout you will be looking at several months before you can put anything interesting in the tank, but that's how to do it on a budget. Going faster safely requires deeper pockets.