Uh ... to be honest, you should just be trying to get someone who will contribute at the major league level.
More than any other major sport the MLB draft is a crapshoot. It seems like the expectations are low for this number 1 pick but as was pointed out it wasn't a great draft and maybe they expect him to contribute more than I know.
Here is the history of the Nats number 1 picks:
2024 - Seaver King
2023 - Dylan Crews
2022 - Elijah Green
2021 - Brady House
2020 - Cade Cavalli
2019 - Jackson Rutledge
2018 - Mason Denaburg
2017 - Seth Romero
2016 - Cater Kieboom
2015 - Andrew Stevenson
2014 - Erick Fedde
2013 - Jake Johanson
2012 - Lucas Giolito
2011 - Anthony Rendon
2010 - Bryce Harper
2009 - Stephan Strasburg
2008 - Aaron Crow
2007 - Ross Detwiler
2006 - Chris Marrero
2005 - Ryan Zimmerman
Successes - Zimmerman, Strasburg, Harper, Rendon
Contributor - Detwiler, Giolito (Got us Adan Eaton; Had a couple of season with the White Sox), Fedde (this season so far for someone else)
Busts - Marrero, Crow, Johanson (who), Stevenson, Kieboom, Romero, Denaburg,
Jury is Out - Rutledge, Cavalli, House, Green, Crews, King