How exciting - a blank canvas! Mine had to be cleared of leylandii, elderly shrubs, and undergrowth first before I could assess the space. Then I used a large notebook/ringbinder to record thoughts, ideas, and photos.
First, I discussed with my husband what we wanted the garden for. He said he wanted somewhere nice to sit and vistas to view (! our garden is very small!). I wanted to be able to pick my own fruit and vegetables, and have colourful climbers on the walls and fences, amongst lots of other things. What do you want to DO in the garden when you're not actually gardening?
I think that Autumns and Winters are actually the best time to prepare the 'bones' of the garden, with shrubs and trees and any hard landscaping. And besides the bulbs for Springtime, perhaps you could put in some instant colour with pansies and primulas, for example. Find ways of stocking the garden without spending a fortune. Don't forget to keep a record with regular photos. I agree with Hollie-Hock; It's a long-term project, can't realistically be done in one year, if ever, and I have learnt to be much more patient! Just enjoy all the processes, including just looking at it.
A book I found very helpful was 'Creating Your First Garden' by Paul Thompson. He also calls it 'Virgin Gardener'.