The grass - you can make a loam stack by stacking the chunks of grass you dug up earth to earth, and grass to grass iykwim? In a years time it will make for beautiful potting compost or soil enricher. With the 'hole' left top with multipurpose compost (or home-made compost if you have a composter).
Try companion growing. Dont do too many potatoes. You dont have a huge plot and they take up quite alot of space (considering they are pretty cheap to buy in the supermarket). Grow things that are more expensive to buy, and full of flavour when freshly picked.
Try a few of the following, depending on your taste: Courgettes, sweet peppers/chillis, basil, thyme, parsley, chives, mint, rocket, cut and come again lettuce/niche mixed leaves, little gem lettuce (small and gorgeous), rhubarb, squashes, beetroot (absolutely gorgeous), dwarf beans, Broccoli, spinach (so easy), cherry tomatoes, aubergine. Dont forget fruit - figs, raspberries, blackberries, blueberries (absolute must), strawberries. Fruit are, in fact lower maintenance. Once planted they stay there.
Carrots are cheap to buy in the supermarket, but the flavour of freshly grown is sooo intense its worth growing some of those.