Not at all. I only got my first greenhouse last year and I've been gardening for 60 years.
You won't really be able to start seeds off to grow much this year other than some salad leaves, herbs and so on, but next spring you will be able to fill your garden with veg. Light and sandy is perfect for carrots and onions and garlic. You will really be able to grow just about anything in your garden, though you will have to keep an eye on the watering.
If you like fruit such as gooseberies and blackcurrants or rhubarb, you should be able to find these for sale in pots any time now.
The greenhouse is fantastic for things that need just a little more warmth than the garden offers. Tomatoes, peppers, aubergines.
You can start to buy seeds now ready for next year. Go along to a good garden centre a family run one if there is one nearby, and they will give you lots of advice about what is best for your area.