Mushroom Kit - Can I reproduce the spores?

I bought a mushroom kit today, the idea behind this is if it goes well then I'll try the 'exotic' mushroom varieties.

There's 2 bags in the kit - one is a base layer of some type of compost and the other is a top layer of innoculated spores.

I'm wondering about a thin layer of worm-poop in between - what do you think?

I'm also wondering how to increase(?) the life of the mycelium spores - is it possible to allow this to reproduce and so to have a longer production?

The minimum performance I need is to have at least £6 worth of mushrooms had I bought the same quantity in the shops. Ideally double would be great. Have you had a good performance from your mushroom kits?

Many thanks for reading me and your time to post!