If you think your serious about this I would buy a small polytunnel, 3m x 2m should fit in nicely by the shed
Buy one of the blowaways as people call them and just install it well.
Best is to dig a trench, put the excess material down into in and then fill the trench back up.
Then add some extra weight, raised beds you can connect to the tunnel, or a few slabs overlapping the bottom metal etc.
Should be fine without if installed well but it gives you some backup just in case.
If its slightly dodgy weather outside you can have loads of time in them, plus they will be warmer due to trapping the sun energy.
Mine is often hitting 20 when its 5-10 outside.
If in 3-4 years you find your still into gardening and you enjoy it then swap out the poly for a decent greenhouse.
My original poly (still going strong 5 years in and its in a very windy spot) I have raised beds in it with a small path down the middle. Works well.
Means more watering though so consider that factor (applies to all raised beds, but especially in a warmer environment)
A poly will bring the start of the season forwards, and push the end out. Plus you can do some overwinter crops in them as well.
Pots work really well as opposed to raised beds and means you can move them in and out.
For seeds, you can harvest some, so tomatoes, chillis etc.
Or maybe ask around a bit and see if you can find someone else who self grows. Most seeds packets are way too large even for people with allotments so you may find you get given some, or can share a few packets.
Aim to grow stuff thats either expensive, or is hard to come by. Plus check its yield to space. Some things take up way too much space and are really poor value in limited space!
