The brand of filter doesn't really matter much, even the stock one is just fine. The importaint thing is to make sure you keep it clean and welll oiled with real filter oil (regular motor oil is not sticky enoug to keep dust our of your engine).
Gear oil is a topic of much debate, you can use 10w-40, 80wt or Automatic transmission fluid and your transmission will be just fine. Again, its more importaint to change it regularly than to have the absolute best oil.
I would go with the 9, or even a 8 (if you riding is mostly slow going) plug (I like the BR9EG or BR9EIX much better than the ES models as they have a finer electrode which doesn't foul as easily. However, if you are having trouble with it fouling or the bike is loading up and smoking a lot you should lean out the carb jetting a bit. The air screw on the side of the carb can make small adjustments in the 0-1/4 throttle range, the pilot works from about 0-1/2 throttle, the needle (adjustable by moving the clip up and down. Clip up = needel down = leaner) works from 1/4-3/4 and the main jet from 1/2- fully open. All of the above are easy the change and very cheep (~$2-$3).
good luck:)