Depends on your goals for the tank. With higher lighting (moderate to high, >30 PAR) it's recommended to use pressurized CO2 injection. Some start with liquid carbon dosing like excel. But the recommended dosing on the bottle is geared toward low tech, low light tanks. When you start getting into higher light territory, more available carbon becomes more important. So you'll need to dose excel in higher quantity than directed. Excel can get real expensive in that regard in a larger tank like yours. Luckily, there's a much cheaper alternative to excel. You can opt to start with metricide 14 which is basically generic excel. In the hobby we call it "glut" short for the active ingredient Glutaraldehyde. It's about 2x stronger and way cheaper if you buy it by the gallon.
So I'd start with the goals of your tank, then buy a light. If you aim for medium light or above, and have the money, get a pressurized CO2 system. Aquatek makes good quality regulators for the price. If you're not ready for it, you can start with glut.
Lastly, you need a good fertilizer regimen for moderate to high light tanks. Dry ferts from GLA are best. I dose with the pps-pro kit they have.
