A big question!
I think you need to plan what is going to be grown first.
For example, you might have an area for annual vegetables. This will be an 'every year' cost in seeds (tho' you can save some from the first year's crop)
You might also have a perennial area (soft fruit, top fruit, herbs etc). But rather than trying to bring it all under cultivation in the first year,it might be worth starting with a nursery area, growing a few of each crop, and multiplying them up from cuttings/offsets/root division etc. This will be a 'once only' cost. In the mean time, the rest of the ground can be mown to control weeds, or sown with green manure, or cleared by chickens.
Remember that you can get much better seed prices by buying in bulk from trade suppliers.
An exciting project!
