I am looking at multiple builds with different abilities and I don't know much about the powersupply. For instance if I had a build with 450 watts and I was planning on overclocking, would be the best wattage for the power supply? Also, Is bronze certified good enough or is it worth it to pay for a gold+ powersupply. I am on a bit of a tight budget so I am looking for any way to cutback price on the build even though I've heard you should never cut price on the powersupply.
It really depends on your gear. If you are building an Intel based CPU and a single video card then any good quality 500 or 550 would do just fine. There is a pretty great deal over at Newegg for the XFX 550 watt that would be great for now and future upgrades if you needed it: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
You shouldn't go too cheap on a power supply, everything is dependent on it. There are plenty of well manufactured Bronze rated supplies, that just lets you know how efficient they are. Saves a few dollars on the electrical bill.
XFX 550W is a popular choice. Seasonic, Antec, Superflower, and the more expensive EVGA and Corsair are made by good manufacturers.
Overclocking power ratings are difficult to measure, depends on the configuration of your system. Even then it varies by the individual chips (CPU/GPU/RAM) you receive and what voltages you have to run through to get the desired results.
Haswell chips nearly double their TDP on a high overclock. GPUs vary wildly, but you can often go by the max value of the input to the cards (Slots 75W, 6pin 75W, 8pin 150W. So a GTX 780 Ti or R290 'could' pull a maximum of 300W. Again those are maximum estimates, the wires used are generally underrated.
Best thing is to find benchmarks from similar builds on this website and places like overclock.net to get real world values.