Hi Jacob,

My advice is to spend two days cycling to Geilo using the nice mainly gravel route to Gol and onwards to Geilo.

https://ridewithgps.com/routes/42481740?privacy_code=eJFTaU64G40hQxaj (Oslo – Gol)
https://ridewithgps.com/routes/42481662?privacy_code=MYoBekbvEAPSt4QK (Gol – Geilo)

I think Flå could be a good place to spend the first night. There are hotels and a free shelter not too far away: https://www.google.com/maps/place/Fiskesø+med+Shelter+og+toilet/@60.4250586,9.413113,14z/data=!4m15!1m8!3m7!1s0x464068be513bb3b5:0x205367fc31a5efd5!2sFlå+Municipality,+3539+Flå!3b1!8m2!3d60.3837212!4d9.4859049!16zL20vMDE4NzZ2!3m5!1s0x4640654e5bdf0a2b:0xc80f0463ae11a653!8m2!3d60.4338099!4d9.4103906!16s%2Fg%2F11k10_7j5v

From Geilo I would follow the route here to Rauland. This goes over Hardangervidda (gravel mountain pass) but you can skip it and stick to the valley if the weather is bad. https://ridewithgps.com/routes/42687633?privacy_code=qfHZyrJql6q6Qv47

From Rauland it’s up to you really. The roads are reasonably quiet in these areas. You will see some of my route suggestions to get to Kristiansand here: https://cyclenorway.com/routes/norse-all-road-series/overview/

You will find many of the routes mentioned are on gravel or quiet roads and these really are the best to cycle with a gravel bike. Wild camping is pretty easy to do but there are also towns available to resupply and find accommodation.

I think you won’t have too many problems completing this in your time frame with what you write above. But it will be a tough hilly route with plenty of elevation gain.

I hope this information helps. It’s a beautiful area to cycle.