First of all, there is another simple way to attack creatures. Just move against them! It will automatically make you strike with your equipped weapon(s).
Spears and such do not alter "k" or "Z" damage, because "Z" consists of your spells and "k" is your "kick" so to speak. Either "Alt + q" or "Shift + 2" will let you see how much damage your normal attack and kick does.
To sell things, just (d)rop them. To buy things, pick them up (,), and then walk over next to the shopkeeper and (p)ay for them.
For the genre of this game, Its a rogue-like. And yeah, its really fun. If you have anymore specific questions, just ask. Most of our helpful threads drop off the first page rather quickly anyways.
Normal - GE Ranger, Human Monk, GE Wizard, Hurthling Beastfighter, Hurthling Farmer
Ultra - ULE GE Wizard