the minimum specifications for running arcmap in a windows environment are ridiculously low...2 Gb of ram (really!?) ...4 maybe...8 comfortable, 16 good 32 no problems. and that is memory after everything else has used what it needs. Storage space isn't the issue, you can get X Tb external drives for next to nothing...what you don't want to do is get into a situation where processing is being swapped out to disk in order to complete.
Many will recommend Mac environments that work for them but you have to weigh the cost of upgrading a system versus just buying a Windows-based system for desktop work. For field work, the camp is divided and you have to weigh the need to do analysis in the field (not just simple mapping) versus the cost of doing so. So check the online help or this site using
ArcMap System Requirements the highlighted link is for 10.3 but they haven't changed significantly
