If the news is anything to go by (plus bloggers etc), many new people are going to start gardening this year. I wish them well but they need to realise it isn't as simple as sowing things and hey presto, great vegetables and fruit grow. They need food and water, possibly staking etc.
It is always best to only grow what you will eat. Start with a few simple things and see how you go. There is tons of help, especially on You Tube, as well as books, tv, friends etc.
Many will unfortunately sow too early, not realising about frost (or plants getting too tall and spindly indoors because they need to go out but can't). They may have a bit more knowledge and sow later but haven't got around to frost protection such as simple greenhouses/fleece. Tender plants, such as tomatoes, cucumbers, and certain other vegetables, fruit and flowers, need protection until the last frost dates for their own area. The weather has changed so much in recent decades, that sow by dates, dates of last frosts may well have shifted backwards.
Bugs will have a feast, animals will dig up, pee or poo over them, that's if they don't eat them down to the ground. Only perfect items are usually available in the supermarkets and home grown are all shapes and sizes with various problems. Things take a long time to grow and I feel many will just give up. Please don't!
I have been gardening close on 45 years and still have failures due to pests or adverse weather conditions. The heat wave last year was such an example and if it happens again, I will need to shade my raised beds.
I once made the mistake of saving seeds from supermarket tomatoes not realising they were F1 hybrids and often don't come true from their seeds. They were fine to eat just not the good flavour of the original. Also they were grown in greenhouses and I didn't have one. I used to sow tomatoes in February, now I don't start until the end of March. Our last frost dates have shifted backwards over the years we have been here. I used to be able to put the resulting plants out beginning of May, last year it was the beginning of June!
If you want to seed save, look for non F1 hybrid seeds, or heritage seeds, they usually come true from saved seeds and saving your seeds, where possible, will save money the following year.
Know your garden, where does the sun rise/set. Where does the shade move to and from. How will you water it, can you set up water butts/old dustbins or other large containers to collect rainwater, to save using the hose pipe. We currently have 5 large water butts and one old black dustbin. We ran out of water last year so are adding two more black bins to our water saving area.
Soft fruit is a particularly difficult thing to grow here. They always do well for a couple of years then start to die, despite testing the soil and adjusting the nutrients where possible. The exception is the blackberry, a real trouper!
Read, watch and listen, then read and watch some more. Weed, feed and water. The first year may not save you much money but if you have success, it will taste so good you will realise what you have been missing. After the first year, adjust your mistakes, feed the soil, keep going and you will enjoy the harvest and it will get cheaper.
Be brave, get going but don't give up at the first hurdle. Babies take an age to turn into adults, vegetables and fruit are the same but on a shorter time scale.