Trusses are amazingly inexpensive, or at least I thought so after I built 3 of them myself. The thing about trusses is that they all have to be absolutely identical, or your roof will look more like a wave slide than a roof. They don't cost much to buy, and the nice company that delivers them will usually set them right where they are supposed to go if you schedule things right. NO LIFTING! That's a good thing.
What's more, a pole barn means these trusses are very very large, and not something to play with if you don't really know what you're doing. As a general contractor, I know to hire a sub.
Framing the rest of it is pretty straightforward, make sure you provide tiedowns in the foundation per local code, (usually consisting of a combination of bolts and straps), a sill plate of pressure treated lumber, and framing members every 16 inches on center.
I can't design this for you, and you really should have a licensed and insured architect design your project, so you have something to show your local building permit application reviewer.
If you do things by the book, with all the proper local supervision, they will make sure you do everything right. Get real plans, and hire subs for the parts you can't do yourself.
Or get a general to do it all for you and that way you won't have to buy so much excedrin and band-aids.