You probably need to decide if you want to go Classic or new hardware direction.
Check system requirements for available software on
http://aminet.net You will need something with a 020 or better. so looking at a1200, a3000, a4000
Probably easiest to get a a1200 but you would want to then purchase a good accelerator. (this can cost same amount or more than the computer itself but worth it if your a dedicated fan aka nuts (: )
If more serious about performing work, then might be better to look at new generation hardware X1000 (not yet released budget hardware) or x5000
You may want to test out AmigaOS under emulation like WinUAE first to get a taste for what you are getting yourself into. Actually this would be a cheapest option, just setup a machine for emulation.
Theres a few youtube videos around about using Amiga today for work.
https://www.google.com.au/search?q=using+amiga+today&source=lnms&tbm=vid&sa=X&ved=0ahUKEwimhvHRyM3TAhWBupQKHfvJCx8Q_AUICigB&biw=1745&bih=828
