Lighting for 2 x 2.5 x 4 foot reef tank

Hi guys,



As in the title I have a 2 x 2.5 x 4 foot marine tank. I only have three corals but am wanting to get really serious about reefing and begin to fill up my tank with a gorgeous range of corals. Unfortunately I have no idea what would be an appropriate lighting for a proper reef tank, especially considering that my tank is 2.5 feet deep.



My current lighting is only a 27 watt LED lighting which is 120cm long. This works great for my fish but will do nothing for my corals.



Also, I don't want to spend an absolute fortune if I can avoid it lol



Any advice??? Thanks!!!