It all depends on how much space you have and how many plants you want to grow.
If your planning on growing a plant or two...then a CFL (Compact Flourscent Light) system would do just fine. You'll probably need around 100-200 watts of light to grow them nicely....but remember this....you can never have too much light! What you can have too much of is heat. It's very important to control the temps of your environment because heat stress can kill or hermie (create seeds) your plants. The advantage of CFL's is that they don't create much heat...so a ventilation system won't be necessary. Furthermore, a ballast is NOT required for CFL setups. A decent setup should cost you around $100 bucks.
Now if your planning on growing more than a couple plants, and you want decent bud, than your probably going to need a HPS (High Pressure Sodium) or MH (Metal Halide) Setup. These are the most popular setups amongst growers because they produce the best results. They're also very energy efficient. A 400 watt HPS light produces the same lumen output (light power) as 662 watts of CFL's. Since HPS and MH bulbs are not your "standard" sized bulbs, they require a special socket and ballast. By managing the amount of current in the electrical circuit, the ballast is used to control the power coming from your wall socket as it surges towards your bulb. IT IS ESSENTIAL! You can't run a HPS or MH bulb without one. But these high power and energy efficient lights come with a big cost.....heat. They produce alot of heat. The bulb and ballast produce enough heat to where a proper ventilation system is required on most setups that are 150 watts or more. If you have the funds, the space, and the desire....than a HPS or MH setup is definitely the best route. A decent setup will cost around $150 or more.
As far as ventilation systems go...it all depends on your temps. You'll always need a fan blowing fresh air into your grow room and you'll definitely need a fan blowing the hot air outside the grow room. After this, if your temps never rise above 84 F, than that's all you'll need. But if it ever rises above that, than you'll need to install an A/C system or inline duct fans. Most HPS and MH growers use reflectors that have "air cool fittings" so they can attach ducting. The ducting also needs an inline duct fan installed to suck the heat away from the light and blow it outside the grow room. Unfortunately, these inline duct systems can be very expensive...
Hope this helps!