Ram upgrade queries

My question being is my current mac has 4gb of ram and i am looking to upgrade in a hope that this will slightly improve performance. I have no major issues with my mac and have been very happy with it since purchase from new. However recently it has slowed a little and when running football manager 2013 for example the game action runs extremely slowly to the pouint where on occassion it is virtually unplayable. I also from time to time am experiencing the rainboiw wheel more and more

I am considering one of two upgrade options. Upgrade to 16gb and if i do so is this better to do so with 2 x 8gb or 4 x 4gb or does it make no difference what the slot configuration is?

Second option is to upgrade to 12gb with the two existing 2gb remaining and add two x 4gb

I am considering the upgrades with crucial which seem reputable and decent quality from reviews. Price is not really an issue as the max is around £60 or so with crucial it appears

Would be interested in experiences and comments on the above please

Thanking all in advance of any replies