Heres what im doing and maybe you can get a little insight to begin on.
I know where your coming from on the cost thing, but one thing i have learned is do it right the first time and never worry for relap projects.
Things I buy are relatively cheapper way.
1. When i go looking for drywall i all ways ask to see what scrap they have for sale. Most likely you will find a few deals on drywall, you may have to cut 10" off, but the price will be significantly cheapper. There may be a gash here and there but if theres no seriouse damage why not.
2. I purchase 16pound bags of unmixed joint compound. Its very easy and very cost effective. Why buy a 1 gal pre mixed for $7 when you get more from the unmixed and only pay $4. All you have to do is add water.
3. And for the do it yourselfers, there are endless amounts of research on the web. Home depot key word, they have information on step by step instructions. And you also have people like tomh who have been doing this before i was born probably who can guide you each step of the way.