There's a belief that gardening can cost a fortune but growing from seed can save you a fortune. It also opens up a potential to sell or barter away access, and if you can't do that you can learn about composting instead! Growing seeds also teaches you what some seedlings look like and stops you from weeding them out in your open beds in the future. We are a frugal kind of couple and have in the past used old fruit crates and tyres as cold frames. All you need is a piece of glass and walls for your cold frame, tyres give you a lovely insulated circular wall. At present, we're sowing wild garlic, spring cabbage, primroses, hops and winter lettuce in the glass house. When it gets too cold they'll go under fleece or into a cold frame. The cabbages will go into open ground at the end of September and will also be fleeced if the weather is bad. Most hardy annuals and perennials you can sow now as long as you give them a place where frost can't strike at them.
Sowing seeds will change the way you garden. Even growing on your windowsill will change the way you grow and eat. You can grow spuds in a cold greenhouse to have spuds for Christmas, just put them in a large pot or old compost bag and keep earthing them up by raising the level of soil in the pot or bag. You can plant flowering bulbs in September for next spring. Plant garlic too and have a lovely tasty garlic crop next June. You can sow greens in the ground as long as you cloche them - a cloche can be as simple as clear plastic over hoops made from old plastic piping or a garden hose or even bamboo canes. A cloche doesn't have to be semi-circular it just has to do the job. The idea is that you start to grow for winter as well as summer, and you may not get the same gluts as you got in high summer but a plateful of spuds and greens from your own garden will make you smile in the depths of winter. If we can do it, then we can all do it in any space we have to hand. Never underestimate a good windowsill.