The problem with supermarket herbs is that they are too tightly packed to survive for long. However I've had reasonable success with both parsley & basil by splitting and replanting as soon as bought...Morrisons were selling them at only 50p a pack recently. The other option is to sacrifice some of the seedlings for the sake of the rest, so thin the pack out by about 50% then pot up into large pots and cross yr fingers.

As Val said, Mint is very invasive, so people usually plant in pots , however it very quickly gets rootbound and then top growth is reduced. You need to get into the pot and pull away loads of the thich roots then repot some of them, they will quite quickly produce new plans.

I don't use a lot of mint in cooking, the usual mint sauce and bits on potatoes, but I do make a lovely salsa with it, which isn't overbearingly minty and goes lovely with cooked chops and steaks.

Pleased to be of service..