You can do pretty mucheverything, if your mate doesn't do the same as you.
For fun I'd go for two different sorces, you being cold/fire/light, and the other being one of those, just not the same element. That way you would me able to farm items fast (tele), kill bosses frikkin fast (static field) and have a lot of fun.
I'd go try getting insight polearm as early as possible, if you make it in a 4 sock scythe or something you can even wear it yourself!
Try make those low runewords, spirit, lore, stealth etc. Notice if you're doing this on singel player, you need some kinda mod.
The best duo with sorces would be fire and cold. Then things will drop REALLY quickly. Fire will roast andariel in a couple of secounds, blizzard will do the same with mephisto (with static field for mephi).
Remember to put those points in the 1 point wonders, tele, static, shiver armor etc. I would not suggest going for energy shield unless you have some points in telekinesis.
If you do encounter some fire/cold immunes static first their health down, then let your mercs encounter them while you use telekinesis for knockback. They should fall quickly enough.
If you're having trouble getting the stuff for insight, run countess in normal! She often drops tals, rals, tir, etc. The Sol should you be able to get for some PG's. The 4 socks polearm.. a crappy one is worth very few PG's too.
If you ever find a spectral shard, be sure to use it until you find something that beat it! 50% FCR is very nice, along some res and mana.