Bad news - there is no shared chest like in Sacred 2. To set items aside for other characters you have to set up a multi-player LAN.
Never done it myself so I can't really help, you'd have to dig through some older threads.
For a melee character I'd go with a Soaring demon build - EPOX has a great guide. Dwarf is fun, theres a good vehemance and dwarven steel build posted - basically pump dwarven steel which reduces enemies physical resistance. Haven't played the vamp that much. Wood elf is fun with multi arrow and thorn bush. Poison mist dark elf is a great leveller, kills bosses easily but is a bit boring.
Battle mage with water magic /ring of ice is good in the sense if you have bad regen times you can hide behind it, let monsters come to you. You get multiple Life leech, you can use split, and if when you hit someone with gust of wind they don't get knocked back as much. Gust of wind is poison damage which some monsters have low resistance too - Orcs iirc and Sakkara demons in UW.
when you get to higher difficulties it isn't necessarily raw damage but resistance - so if 2 weapons did the same damage but one has more magic damage vs the other with more fire damage, then fire will do more damage vs ghosts.