Upgrading PC RAM.

So I want to upgrade the RAM on my PC to use particular bits of software that I currently can't use.

I'm currently on 6 GB of RAM and want to boost up to between 10-12. The most RAM required by the software is 8 but I want to go over so I can run smoothly.

Down to the bedrock of my post, I don't have a clue what to be looking for when searching on sites such as Scan for RAM. So what should I be looking out for/what should I get.

If it helps I don't really have much of a price range as I have a job as well as my student money so I can afford almost anything, just not ridiculously expensive of course

How many memory slots are there on your motherboard? It would be good to tell me your motherboard model so I know your max. amount and other things.

I'm 90% sure there are four slots and two are currently being used. The Motherboard is a Packard Bell ixtreme M5860

The motherboard used in your system only supports up to 8gb. So in reality, upgrading your memory will not do much at all.
If you really want to upgrade; I would suggest a new motherboard and purchase your RAM later on.