What flavor are you vaping? And what nicotine level? I never feel satisfied on fruity or foody flavors - they actually do the opposite to me and make me feel like I ate. Have you tried a variety of tobacco flavors? Vapor4Life sells a lot of filled cartos for KR808D-1. I think their WOW 555 is nice. I haven't tried many but they have a WOW tobacco sampler and a couple of other tobacco samplers. They also sell empty cartos - I like their Coolcarts.
I can get by with good TH and hardly any flavor (like Dekang PG juice) or medium TH w/ comforting tobacco flavors. I like Turkish blends (often called Camel, or Desert Ship, and I think Dark Vapure and DK-TAB are turkish blends).
If you fill some of your own cartos, FreedomSmokeUSA has a lot of tobacco ejuices. Only some are available as sample size and samples at fixed PG/VG and 24mg only. In their normal Tobacco section there are lots more and the smallest bottle is $4. Lots of tobacco flavors.
And BTW - something else you can do with KR808D-1 battery is put a DSE901 atty w/ 901 carts or drip tip on it (or 510 atty using an adapter and 510 carts or drip tip). The KR8's battery is equal or superior anyway so it's a fairly cheap way to try carts (and dripping if you have manual batteries because they have the hole in the end blocked off). Just something to keep in mind.
And BTW - if you need to buy any replacement parts, verify that your unit is indeed a KR808D-1 then don't pay more than $18 for a battery. Some rebranders charge up to $50 for a battery.