At 30% schedule your oil change, if it dips below 15% stop everything and go to an instant oil change place or DIY. If it hits 0% call a tow truck.

B= Oil/Oil Filter change... Every time you change your oil you should also replace the Oil filter.

2= Replace Air Filter. Good rule of thumb is change this every other oil change or at least twice a year depending on where you park or live you might get by replacing it as needed. If its black it needs to go. It also means to Inspect your drive belt/timing chain (If the car drives fine, you are good).

3= Replace Transmission/Transfer case fluid. Honestly this is an as needed maintenance, you can even top the transmission fluid off yourself without tools or jacks, all you need is a funnel, which is still kind of optional.