The key is to find the hardware requirements necessary to support whatever OS and/or applications being installed.
Generally most software lists the hardware requirements in some categories such as minimum, recommended, or best.
You do not want minimum. Recommended may be okay but optimistic. Best is likely "best" with respect to performance but likely to cost much more.
Some combination of recommended and best is probably going to be good balance between performance and costs.
For example here is a link that addresses Windows 8 requirements:
https://www.lifewire.com/how-to-upgrade-to-windows-8-2377757
Always a good idea to check other sources to verify.