Don't bother trying to CPU or GPU mine any SHA256 based coin. ASIC has ruled those coins for a FEW years now, GPUs aren't even in the same ballpark any more and CPU mining them is a sad pathetic joke.
Don't bother trying to GPU or CPU mine any Scrypt coin. ASIC have ruled there for about 2 years, you'll just lose a lot of money - even with free Electric, you'll probably have your GPU die before it can mine enough to pay for itself, and CPU mining Scrypt is even a worse waste of money.
Non-SHA256 non-Scrypt coins (X11 coins like DASH for example) CAN be GPU mined for a profit, but it's a very slow low-profit option and starting to get a bit iffy if you'll even manage ROI even on those coins unless you have VERY VERY cheap electric.
I don't know of any coin that is viable to mine with a CPU but I've not really looked hard for one.
I advice you don't invest time and money in shitty altcoins.
For now your best option is ethereum, and if you want an advice, don't change them quickly.. let the speculation do its magic.
Funny how your 2 sentances contradict each other.
How to mine x13 with Gigabyte Radeon HD 6850 1024MB GDDR5?
Don't bother, you won't make any money with gear that old. Upgrade to a Maxwell-based Nvidia or at least a fairly CURRENT AMD card if you want to have a chance to make a profit even on GPU-mineable coins even if you have VERY VERY CHEAP electric. 7xxx series and preferably an R9 series AMD is the minimum to have a chance at a profit, and you have to be very carefull with the 7xxx series to get them CHEAP.
