Avicularia Avicularia housing requirements?

Hi I have a female Avicularia.a housed in a 14x8x9 terrarium and have a few questions. Should I get a taller cage? If so then why will it benefit the tarantula in any way? If so how? and is a temperature gradient of 70 to 80 degrees sufficient for it? If not then how can I heat it? Why does it matter?And what can I use to measure humidity for a reasonable price? Whats the best kinds of substrate? Will forest bark do the trick?