Have at least two screens. Have more lights. Have a good ergonomic gaming-like mouse.

Screens should be 2+, not 1(unless it's huge and ultra-wide, hence more expensive). Mouse should be with high DPI and 7+ buttons programmed as shortcuts (specially if you have two BIG screens). Lights should include a workstation-specific lighting with individual control. Screen brightness ought to be a function of indoor lightning's brightness, which should be high, and a function of outdoor brightness and time of day (independently). You are likely to have less lighting than optimal, most work environments do. My therapist said I must not talk about monitors heights anymore.

Don't know much about the what's the proper angle between screens, willing to hear an informed opinion. I recklessly use 20 degrees.

Spend money on ergonomics is not correctly phrased, most people haven't a clue about how ergonomics ought to be. Spend time(researching) on ergonomics it's a better slogan.

A few studies:

Veitch, J. A. (2012). Work environments. In S. D. Clayton (Ed.), The Oxford Handbook of Environmental and Conservation Psychology (pp. 248-275). New York: Oxford University Press.

Veitch, J. A. (2006). Lighting for high-quality workplaces. In D. J Clements-Croome (Ed.), Creating the productive workplace (2nd ed., pp. 206-222), London, UK: Taylor & Francis. http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=shwart&index=an&req=20377130&lang=en

Veitch, J. A., Stokkermans, M. G. M., & Newsham, Guy R. (2013). Lighting lighting appraisals to work behaviors. Environment and Behavior, 45(2), 198-214. Available at: http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=shwart&index=an&req=21268291&lang=en

Veitch, J. A., Newsham, G. R., Mancini, S., & Arsenault, C. D. (2010). Lighting and office renovation effects on employee and organizational well-being (NRC-IRC Research Report RR-306). Ottawa, ON: NRC Institute for Research in Construction. http://doi.org/10.4224/20374532.