Are they not double pouches? If so then 6 on the vest and 1 in the gun should be plenty. If not then you could get some extra mag pouches and put them on the belt of the vest.
You can get army surplus chest rigs for around £18. 3 Double pouches and two very spacious utility pouches to put all your other bits in. Failing that you can put plenty of magazines in the side pouches as well.
But its really annoying to run with them in the pockets. they also move around bang together and make noise. unless you have the special ones with the elastic bands on the inside to hold them togeather