Where to begin with growing veg?

For a easy start to the salad season, look for 'living salad' in supermarkets. it tends to be available from about now and gives 60-70 plants which can be transplanted in to pots or troughs for earlier crop.It will give you a start while your sown seeds follow on.
Learn about picking lettuce leaves from plants while leaving the rooted plant to grow more leaves, this will extend the life of the plant by 6-8 weeks, give you 3or 4 times the numbers of leaves and less gaps in production.