Most can go straight into the ground but I grow Tomatoes, Cucumbers, Chillies and Peppers in pots first then plant out in grow bags. One tip I got a few years ago is plant broad beans in September/October and you will have an early crop the following Spring. My garden currently consists of (including the above) carrots, cabbages, cauliflower, broccoli, radish, parsnips, spring onions, spuds, runner beans (including dwarf runner beans), beetroot, strawberries and various herbs. Nothing like home grown.