I'm about to go on my first adventure today. I will leave in about three hours for about a 150 miler. Maybe longer if I really want.
I am using my existing mtb with some minor road upgrades and some special stuff that I had to buy, panniers and stuff. I'm using some of my normal camping gear, with the exception I had to buy a smaller tent and stuff like that.
Total price of the "other" stuff...about $200.
And if I enjoy myself there may be some future upgrades.