Since you are just starting out, I wouldnt recommend using the MVBs. From the tests Ive run, there is really only one brand worth the money (taterbug, remind me to PM you about the Arcadia MVB) and that is the MegaRay. Its not cheap, though it will last you a long time. The one I have now is still going strong after a year and a half, and still producing very good levels of UVB and UVA. However, its not an easy thing, nor necessarily a good thing, to use just one light. Its tricky to get both the UV exposure and the heat right with one bulb, and you often end up sacrificing one for the other. They have the High Output T5 fixture on sale right now. The T5 bulbs also last at least a year, and the fixture comes with a free bulb. You can find them here:
http://www.drsfostersmith.com/product/prod_display.cfm?c=6016+6028+25698&pcatid=25698
For the basking bulbs, you can just buy them online at any lighting store for cheap. Try to get the PAR38 outdoor halogen flood lamps. Again depending on your enclosure, you can play around with the wattage, but I think most people use a 75-100 watt. These name brand ones are $7, but you can find cheaper brands for less.
https://www.1000bulbs.com/product/93651/PAR-16751S.html
These bulbs are almost identical to what they sell as reptile basking lamps in pet stores. About the only difference is that the reptile lamps are indoor halogens with a much narrower beam angle (that means less durable so they often burn out much faster, and less appropriate for adult lizards as they dont create very big of a basking area). The light they create is the same, so no need to pay for just a fancy box.
As for your enclosure, building it will always be cheaper. Its just a matter of whether or not you are able to do so. The construction is not very difficult at all, as you are just building a big box basically. If you use plywood, itll take you two sheets to make a 4x2x2 enclosure. Plywood is dirt cheap, and you might even be able to find some that people dont want if you ask around. If you want it to look a little more finished, you can use melamine. Again it comes in 4'x8' sheets too, so a couple sheets will do. I think its a little more money of course, if I remember right its about $40 a sheet. Normally most hardware stores will cut it to your specs, so you dont even have to do that. Just remember with the melamine that you need to get some silicone to seal the edges. It will swell and breakdown if any moisture gets in the middle, so thats very important to finish.