Late September is the sweet spot for Iceland. The summer crowds are gone, camper rental rates drop, and you have a real shot at seeing the northern lights dancing over the black sand beaches of the Ring Road. Driving yourself lets you pull over wherever the scenery hits you, waking up to views of glaciers and fjords without paying hotel prices.
A trip like this usually runs about $4000 for flights, gear, and camper rental. Dropping that much cash at once hurts, which is why some people use a 0% intro APR for 15 months on purchases and balance transfers to spread out the payments over time instead of paying it all upfront.
Keep in mind that the 0% intro APR for 15 months on purchases and balance transfers is a hard deadline, not free money. If you still have a remaining balance when those 15 months are up, the standard interest rate kicks in on what you owe.