You might do better picking the low hanging fruit to gain momentum before you invest in a Zeo and a statistics textbook.

Given that the company behind Zeo went bankrupt and that you need a regular supply of replacement headbands I would advice against going the Zeo route.

If you want something that tracks sleep MyBasis would probably be a better choice. It also gives you other stats.

NeuroOn is a kickstarter product more tailored on sleep.