1)just get that air filter. washable with water. been using it for almost 2 years d. still good!
Just buy the air filter will do? Wash with water without anything else will do? and no need to apply any oil or some other chemical, right?

2)engine oil stick back to recommended oil rating 5w30.. stick with semi-synthetic, service every 5,000km.
as for brand, just stick with branded ones and u shld be safe. dont compromise on cap ayam/neverheardbefore brand.
wrecking your engine is the last thing u would want to do, so dont budget on engine oil! 

3)spark plugs u shld stick back to standard plugs.. unless u have extra dough, go for those fancy-pansy iridiums/platinum and what not..
iridium plugs only change every 3 years/100,000km, but i recommend using standard plug as it is better in the sense that u are using new plugs every shorter interval rather than 100,000km only change once.. (however i gatal last time changed to iridium, now only felt that its a waste of money as my butt dyno dont feel any improvement at all)
Plan to try Denso Iridium, don't mind the no-performance increase though, as it save me more money in long-term. 

other than that, dont forget to follow recommended interval for transmission oil change, brake fluid change, coolant fluid change, battery water and other wear and tear u encounter along the way..
So you don't go to SC anymore?

once u got enough budget, u can plan ahead what else to mod and improve on in the future (but thats another story for another day, plenty more to poison you with    )

p.s : save your money, dont waste on those fuel saving device, 'surbo' crap devices and those unnecessary accessories which most of the time wont work..   

happy modding 

Wokay, thank you!! 

just use water, no need any chemical/oiling needed for works/simota drop in filter.

currently im servicing outside of sc. using better oil & fluids. dont mind the warranty as mine is about to expire soon

Depend on CC. If 850CC then stock rims is 12". 1000cc is 14"