Let me make this statement from the onset: I love Revelate Design’s bags. They are super high quality, well thought-out designs that are stitched right here in the USA. Appropriately, quality of that level costs a bit (sometimes a very little bit) more than other options. This gear would be what I would recommend/use for bikepacking.
If you are an infrequent bike-packer or on a tight budget then you have a few choices. You can make your own gear, rent some gear, or look for some lower cost alternatives. This post is devoted to the latter.
The bike pictured is outfitted with gear costing a total of around $165.
The seat pack is the hugely reasonable Giant Scout Bikepacking bag that runs $69.99. It does not have all the features of the Revelate but it is about half the cost. Inside of the triangle is the Jandd frame bag ($49.95, size large) which will keep your gear in place. This bag is not waterproof so keep that in mind when packing your load. Up top is the Inertia Designs top tube bag ($34.99). I love this option for snacks while on the bike.
The gear pictured, along with a dry bag strapped to the bar with some Surly Junk Straps, will get you through a few days in the wild. FYI, Junk Straps are an absolute must, take a few extra!
So there you have it, get outside and play!