I agree that you're better off avoiding the kit and buying better quality items individually. It will save money in the long run and be much better for the health of your dragon. A big initial investment will be much better than saving money up front and needing to replace things. I suggest getting the largest enclosure you can. I'd get at least a 40g breeder tank but go larger if you can. Building your own is the most economical way to go if you are good at building. This is a popular enclosure build
https://beardies.dreamwidth.org/2145.html Something 4'x2'x2' or larger will last for the whole life of your dragon.
I agree that investing in a high quality
UVB light is one of the best bang for your buck items and is quite necessary. Either the ReptiSun 10 T5 or an Arcadia like this
http://www.lightyourreptiles.com/22-t-5-ho-fixture-high-output-with-arcadia-d3-12-ho-bulb/ are your best bet. They should sit about 12'' above the basking area for optimal results.
Going with a solid substrate is a good idea because it's easy to clean and keep sanitary. I'd start with some non adhesive shelf liner that can be cleaned or replaced. It's a good, cheap option.
For basking, I'd use a halogen flood light or a ZooMed Repti Basking spot light. Having it on an adjustable stand is helpful for fine tuning the temperatures by changing the height of the bulb. The halogen flood light can also be hooked up to a dimming thermostat as well. It's important to have accurate temperature readings so I suggest getting an IR temp gun like this
https://www.amazon.com/Nubee-Temperature-Non-contact-Infrared-Thermometer/dp/B00CVHIJDK or a couple of digital thermometers like this
https://www.amazon.com/dp/B0017N8W90/ that you can mount one on the basking surface and one on the cool side to monitor temps. Adjust lighting wattage/height so the basking surface is between about 100-110 and the cool side is between about 75-80 or so.
You want to include a nice flat place to bask and some spots to hide and have shade. Things like habba huts, flat stones, and flat driftwood pieces work well. There are a lot of ways to go with this so use your imagination and shoot for some places to climb and bask and some places to hide and that will do the trick.