My garden is a mess. please help. I'm on a tight budget!?

I have recently just moved houses and the garden was a mess. There clearly used to be an edge round the garden full of flowers but when we moved in it was covered in weeds. we have just cleared the garden, strimming the gr right back and pulling out the weeds. But the edge is now like thick mud. It sounds stupid but how are you meant to plant flowers in this? Do you just add compost, which is the best kind? I am a complete novice when it comes to gardening. I've just had a baby and my funds are very small. Please help. Any tips on where i can find cheap plants and stuff in Milton Keynes would be much appreciated. I do not have a car so i cannot go pick anything up. thank you. Any help will be much appreciated.