DNA Stage 1+2, not K&N.....The K&N may be a few pounds cheaper, but it seems a false economy, reading the forum. And the Kev fuel Mod, which you need to get the best out of the DNA increased airflow.
The rest of the mods will cost you nothing.....

It sounds like you have the right idea.....you can always add the cans later, which is a relatively expensive purchase, but you could find some nice used ones when the time comes.

correct me if I'm wrong guys, but you would need to adjust your Air/Fuel mixture, to stop your bike running too lean, if you started with just the DNA's. So, first the Kev Mod, then later the filters.