What is the best value for a bus from the KEV airport to blue lagoon and then onto Reykjavic. Are there any packaged trips?
Not sure what you mean by "best value" but you can book an excursion bus that takes you from KEF (not KEV, it's for Keflavik) to the Blue Lagoon and then on into Reykjavik. https://www.re.is/from-airport-to-blue-lagoon/ Advance booking is required. You could also take a cab, but it will probably cost more.
KEF not KEV.
I doubt there are any buses from KEV airport since it is the airport code for a military airbase in southern Finland.
However, as CL noted, Reykjavik Excursions offers service from KEF airport to the Blue Lagoon and then on to Reykjavik.
Here is a link to exactly what you are looking for. Blue Lagoon has transportation for this. You can book both of these legs along with your Blue Lagoon ticket all at once.