1. Anything you would want to keep. lol.. But in all honesty, anything.. You could sell rune packs, you could sell Monarchs for few hundy. High runes are cool and all, but I wouldn't count on making fg around that, it's more of a bonus if you find one. Sell smaller things.. You could probably find 10 monarchs in just a few hours and sell each for 200-300 first day. Sell spirit packs, or try and roll spirits. There are so many options, post some stuff up, see what catches.
2. Any sorc, java zon, pally (smiter/hdin), barb, ne.. literally every class has a starting build, just depends on what you want to grind over, and over, and over again. Focus on lvl 85 areas after you find decent gear in NM/Hell.. NM farming is best for some items like Shako, vmagi, oculus, etc..
3. risk vs reward.. there are more ppl playing softcore, so your chances of selling an item are greater and your chances of not dying are also greater.. If you are not a d2 veteran and you just want to make fg, stick with SC.