Could we do crowdfunding?
why would people be willing to donate money to you to build your own house? i don't get it? Is this seriously an option now?,
"I need something, i'll ask people to be charitable and give me the money to do it"
Anyway.
I researched doing it a few years ago, i'll share those findings 
Land is the expensive part, the very expensive part.
It has to be a proper plot, with building consent etc. you can't just buy a bit of field and stick house on it.
Actual building needs to have plans drawn up, surveys, permissions etc. all this can take YEARS. you plan the build, submit for approval, the council discuss it at the next planning meeting, if the refuse, you have to change, resubmit, wait for approval. so on and so forth.
I would highly recommend a architect for this portion of the job. it is crucial.
Finally when the plan is approved and the land hs permission to build what they have approved you can ask builders for quotes, show them the plans.
meanwhile you'll need to arrange for sewerage to be connected, gas to be connected, electricity to be connected, phone lines to be connected, broadband too if you want it. (all of this costs money)
then the next expensive bit, the building. even doing it yourself your materials will be expensive. even a modest strawbale house will need concrete bases, foundations, wooden joists, roof beams, bales, plaster boards etc. (when we priced ours up, the actual build of a three bed straw bale bungalow was going to cost between £35k and £45k just for materials needed and no labour.
All the while this is going on you still have to eat, sleep, heat and light somewhere to live so you have those costs as well.
we eventually gave up on the idea when we realised our meagre £150k budget wouldn't be enough.
It is doable, don't get me wrong, it just seemed either pay and it's done in 18months or try to do it cheap and it'll likely take 5years plus.
have nosey around:
www.buildyourownhouse.uk.com/
www.selfbuildportal.org.uk/forum/index/1-the-self-build-portal-forum
www.money.co.uk/guides/how-to-build-your-own-house.htm