During the lockdown, there was a surge of interest in growing your own veg, and now we have a resurgence of interest driven in part by the rise in food prices. The price of basics is rising and one way to chip away at it is to grow your own. You do not need a big garden.  You can grow in containers on a patio, balcony even a window sill. 
The cheapest way to grow vegetables is from seed. Seed is always cheaper than buying plants. 

Early March is the time to germinate chillies,  and this is easy to do on a windowsill.
Chillies need a long growing season and to be kept warm, which means chilles can be grown indoors all summer. They make colourful houseplants with brightly coloured chillies.
At the end of the season, you can dry or freeze chillies and you will have chillies all year round for the price of a packet of seeds. How to grow Chillies

I love rocket salad with its strong peppery taste. Supermarket bags of rocket are expensive, disappointingly unpeppery, with a short shelf life. They are also packed in single-use plastic. Rocket, as its name suggests grows like a rocket!  Easy to seed and germinate, pick and come again. Rocket will grow well in a container and keep you supplied with lovely fresh leaves. Definitely on the cheap and easy list- tips on growing rocket.