I went through this a couple of years ago.
First, mapping keys is within the options > Key Bindings in the game. You don’t need outside software.
Second, you’ll do best with a gaming mouse that has 5 keys. They are about the same cost as regular mice, but give you a couple of side buttons you can hit with your thumb and/or little finger.
Finally consider that you have 6 skills, + teleport and potion to trigger. Put you hands on your keyboard in a relaxed positions and see what keys they fall on. For me it’s 2, 3, 4, r, LMB, RMB, LsideMB1 and LsideMB2. those are the keys you set for binding. Since 4 is a little awkward I usually assign a skill I seldom use but want to have available.
Once you get to the Key Binding options choose the skill number you want, click on the named key shown, then on the actual key you want and save.