welcome to the world of cresties.
You'll find that there are lots of different opinions on what you need and don't. I'll make my observations but, no doubt, there will be other members who do things differently.
The temperature gradient is the easiest thing to sort out. By heating from the top there is a natural variation from the top of the viv to the bottom. I have a 60x60x45 for my cresties and happen to have 2 temp probes, one near the top and one near the bottom. (This isn't necessary, but I had a spare lying around so out of curiosity I set it up.) The viv currently reads 21.7 top and 19.3 bottom.
Heating. I don't use a heat mat or a ceramic bulb or therefore a thermostat. Our house stays reasonably warm and all that is heating the tank at the moment is the ambient temperature of the room and a Reptiglo 2.0UVB. I'm trying to simulate the cooler winter months at the moment. During the summer I also use a 25W Daytime Heat Lamp as well. The UVB is on a timer and presently comes on for around 10hrs a day. There are arguments that cresties don't need UVB but I'm working on the basis that I'm going to have a light on during the day, it may as well be a low powered UVB and it can only help rather than hinder their health.
In the evening I use 25W Nightglo bulbs for a couple of hours. These are great for night-time viewing but have one slight issue in that they produce heat as well and the viv therefore tends to reach it's max temperature just before they switch off. I'm thinking of getting some LED strips for night-time, although if the house does start to get really cold during the winter, I can always get the timer to switch on for an hour or so in the middle of the night and keep the viv warm.
A full width exo-terra canopy for the 45x45x60 viv has 2 lamp sockets in it. Just of note; I found that when I had a fluorescent UVB bulb and a daytime heat bulb both in the same canopy the filament bulb would fail really quickly. I'm not sure if it's something to do with how the UVB fires up?
The general feeling is get plently of plants / vines / wood for them to climb on. Both sides of my viv are covered in fake plants and this way they tend not to sleep stuck on the glass with no support for their tails.
I've got a notebook and keep records of max and min temps, what they're fed, what they weigh (every couple of weeks), when the viv is deep cleaned etc. Also if you notice that temperatures are trending too high or low then adjustments can be made.
Hope the above is of help. Good luck and enjoy.