Please note - I am not a mechanic or expert in anything.
Always with servicing and maintenance many start with one of the least important parts of the car. Priority should always be given to brakes, steering and suspension (all three included tyres) then on to visibility (see and be seen, lights, wipers, glass, number plates, etc.) and safety electrics (wipers, heater blower, horn, hazards, etc.).
I go along with what Murdockman has put plus a forgotten but important air filter, if you're looking at and the spark plugs every two years you might as well renew the air filter at the same time.
I'd also look at changing the gearbox oil on a manual box particularly as it's so easy.
Also look after your battery and main cables and connections, keep the battery from getting too low charge and all cable and wire connections clean, secure and protected. If you're going to be doing a lot of short journeys, say under15- 20 miles, and very few much longer journeys then you might want to consider buying an appropriate battery charger or maintenance charger.
As put before don't overlook the tyres even if they have plenty of tread above the legal minimum (which is only really good in dry warm weather) tyres get hard with age and/or lack of use and can deteriorate particularly if the vehicle is kept outside and as I put tyres are an important part of the vehicle's braking, and steering and suspension.
The most important things to keep clean (and clear) are windows, lights and number plates.
Good luck.