Definitely dont skimp on the thermostat. You want to buy something that holds temps well and that you dont have to worry about. I recommend herpstats as thats what I use. But I have had a lot of success with helix and Vivarium Electronics. Make sure its a proportional thermostat and not an on/off type.
Building your own melamine rack would be tge cheapest. Other than check out aninal plastics econony racks amd the racks at reptile basics.