Is this for just paper/plinking within 30yds or actual hunt/pests?
You need some more pellets in various grains and types to really access what your rifle likes best, but I'd try some H&N Field Target(Trophy Power) brass in 14.6, Gamo "red" Power Points in 14.5(Walmart), Gamo Hunting in 14.5(Walmart), and some Ruger Superpoint in 17gr (Walmart).
This is just a start. Some guns in same caliber/manufacturer will like light(er) grains and others like the heavier weights. You never know.
For my Hatsan95 springer in .177, which has about same 950+/- velocity as your rifle, according to Hatsan's chrono test it came with. It shoots the lightweights around the 7-9grains well, but put in some Crosman Premier Piranha 10.5gr and it has great improvement for accuracy. I shoot it around the 25-30yd mark.
Also, it's sensitive to handhold.
For my Diana Chaser 22 pistol/rifle setup, it likes them all from 14.5 up to the Ruger Superpoint 17 grains, while only needing "up" adjustment of the Sightmark Sureshot Holographic sight, but it's also a CO2 and 500fps velocity. I've tried some heavier 17.9 and 18.2 grains, and it will spit them out, w/fuller than 1/2 12gram cartridge but the drop is extreme and just waiting for a squib to happen when using the rifle barrel. I shoot this at the 10meter mark, but at 20yds it's still extremely accurate with moderate punch, using what I know it likes.
I don't hunt or shoot live game with either of my airguns, and if I did it would only be nothing larger than a pigeon. Now, if I got a PCP, that would change.