Start by picking up the rubbish and putting it in the bin, that's pretty obvious, but it will make it look a lot better instantly, then you have to decide what you want from it. Apart from the bush in the corner it looks as though it is all grass or concrete. The simplest way would be to keep it like that, a small electric mower would cope with that amount of grass and be the cheapest option, going over it with a wire rake will improve the grass in time, there are grass seed /compost mixes you could add in Spring to help that.
If you want flower beds, or to grow veg, initially you can get by with a spade and a small hand fork and trowel set. The cheapest spade will not be too much different from an expensive one, but on the fork and trowel set look at how the handle is joined to the blade, that is often a weak point. To make a bed dig out a cube of turf and turn it over, the grass will rot underneath and fertilise the soil some. If you do it now when you come to plant stuff in a couple of months you will find the winter weather has broken down the surface for you a bit.
If you don't know what the bush is it might pay to leave it a bit to see if it is something nice.
Take account of the orientation of the garden and where gets sunlight or is in shade, sunny spots are generally better, but there are plants that love shade too.
Positives, you have good fences by the look of it, that can save you a lot of expense and work and provide good shelter, it is not so huge as to be overwhelming, you have joined a community where you can share your achievements and get ongoing advice and encouragement.
All the best, there can be real joy in seeing things develop and grow.
