If you are trying to deal with money (thousands of dollars), this would be a fairly safe (yet long route). Feel free to change anything, but this is just a general route:
1 Create VM (Linux Distriubtion would be the best)
2.Setup VPN Tunnel (Externally assuming you are bridging network adapters/cards)
3.Install AV & AD Blockers
4.Update Everything
5.Create a snapshot (I'd say once a week update the snapshot with any new OS/AV updates, or before use if you are paranoid)
6.When connected to VPN, load website (if you have a 3rd party wallet like my etherwallet, they have offline wallets you can download that are more secure)
7.When done, close VM

1. Whenever you use the VM, load the snapshot of when it was last updated
   *Be aware nothing is full proof as there are zero-day bugs and exploits
   **Also Diversify your assets (Money/Crypto) so if you do get hacked it won't destroy you