You have a hand slot. You can hold up to 5 gems in your hand at any given time. Others will have to be tossed. Gems CANNOT be placed into your inventory or stash.
Nah, just messin'.
1) Inventory or stash.
2) I'm assuming this will be the case, as higher level gems would be very strong on low level characters. That being said, nobody is going to throw perfect gems into cracked leather armour.
3) I believe so.
4) I think you mean combining. I don't believe this is the case, although gem stats are not finalized on the website.
5) That's up to the developers. Different items will have different max sockets. Correct me if I'm wrong, but I believe sockets roll independent of any other affixes. Also, I think almost everything can have sockets. I am not sure about gloves, boots, and belts. But I know rings and amulets can now.
I didn't know about the gold cost too for upgrading, gold might hold its value yet! So is it gold, plus the artisan has to be upgraded enough to do the upgrade, and multiple gems? Seems like a decent sink!
2.) Are different gems level specific? Like if I get a chipped can it only be used by level 6 an up like in d2.
3.) Do all gems upgrade to the next level with three of the same?
No, you need gold now and to use jeweler
4.) is there any comparing of multiple gems to get the powers of each?
All gems have a required level of 1. Meaning: you can give a new character a max level gem and have him or her just cruise through normal. They intend gems to be the ultimate twinking abilities that make successive runs through the game easier. People will be giving their twinks weapons with Radiant Star Topazes and watch while low level bosses one-hit themselves from the thorns damage. (Of course it will be a long time until people have that high of a level of gems).
All upgrades require 3 of the lower type + gold (and you have to find the recipe to make many of those, as well). That's why, unless botting or duping affects things, max level gems are going to equal untold thousands of hours of playing time.
Sadly no Captain Planet style gem combinations (smashing two gems together would just dilute their purity anyways!)