I do not know which alternative to GDP is best, but there appears to be a useful list in this document - https://www.hks.harvard.edu/content/download/67149/1241406/version/1/file/PAE+Beachy_Zorn_2012.pdf
Appendix 3 begins on p. 77 and provides what appears to be a comprehensive list of the alternative indices that have been proposed. Unfortunately, this document is undated, but the most recent endnotes are dated in 2013.
I suggest you to use the compound Index of "GDP per capita" and "Gini coefficient".
and I should note that Harvey Leibenstein in the first chapter of his book named "Economic Backwardness and Economic Growth" dispute and consider "GDP per capita" as the comprehensive indicator for economic development. and for a perfect index you can combine "Gini Coefficient" with it.