Regarding key bindings and spells, I like to assign my scroll wheel up and down to switch rows (you can't do it in the normal "keyboard" keybinding button, it's the bottom one, I forget the name offhand, mouse axis or something), and arrange things in different rows. Then, for example, I'll have my 3 favorite ranged spells (of different elements) in slot 1 across 3 rows, so simply scrolling up or down switches between them easily. I stick a melee spell in slot 3 and platforms/crates in slot 2.
Once I figured this out, things became much easier for me; far less pausing, no need to drag spells around between slots in combat, etc.