I think what you need to do first is establish how long you will have the allotment for before you can consider what to grow. Contact the landlord and ask if you are to be given a short lease or a long lease shirt leases can be as little as 6 months long leases can be 10 years or more if the allotment landlord is your local authority then they give 12 month leases renewable every year and also you are very lucky where we are they is about a 10 year waiting list

If you cannot get a rough estimate I would try to plant stuff that doesn't cost you much. Try advertising on Freecycle for autumn fruiting raspberry canes - they will sucker and give you lots more for free quite quickly. Many people will have spare rhubarb crowns to give away, though its a bit late now. Most of the stuff grown on allotments is only grown on an annual basis anyway - potatoes, beans, brassicas, salads etc. If you can find anyone who has had new windows put in you can improvise a good cold frame with one or two, or if you want to spend a bit of the readies you could buy a tunnel cloche or two.

If you know anyone with good currant bushes ask them to give you some prunings in late summer. If you put them in the ground most of them will root over the winter and should fruit by the third year.

If it is a short lease Renatefaber you could just grow vegetables that you could eat over the summer.
Glad to see you finally managed to get onto the site.