There are only two things that you need to have a long distance bicycle adventure - one is a bicycle and the other is the determination to keep pedaling. Of course having a water bottle, sleeping bag, and puncture repair kit are useful too, but ultimately don't take too long worrying about what you do or don't need, rather just get on your bicycle and actually start doing it. If you don't have a bicycle, find one, any bike, and don't worry about how good it is.
This particular image was captured in northern Germany as myself and two friends cycled 1,000 miles across Europe on £30 bicycles. Why did we use £30 bicycles? Because it was all we could afford. And we loved it.
Head to Bavaria and love our same journey filled with small quaint German villages, rolling green hills, and the more than occasional large cow. I headed from Fulda (just north of Bavaria) through Coburg to Cheb (in Czech Republic). It's quite a ride and don't be afraid to stray to the forest roads. They have pretty trails, diverse fauna, and the occasional cave.