There should be a twin compartment fuel and oil tank on the machine.Petrol in one side where the pipe goes to the carburettor and engine oil in the other.The engine has an oil pump fitted and the oil then returns to the tank (or should do !!).

I would maintain at least half a tank full at all times.
When the engine is running you should see oil bleeding back into the tank, in spurts. Just take off the oil filler cap, look inside you will see a short stub of pipe just under the cap, this is where the oil should return into the tank. don’t expect a big gush, as it only just comes through in small spurts.

Good luck

You will find a decompressor lever under the frame just below the rotor selector lever, lift this and hold it up whilst swinging the starting handle, when you have a bit of momentum, release the lever when you are on an upward stroke. Just plain unleaded petrol.

Good luck.

I know little about Gems but the simple answer would be that the engine is running in reverse. Not unheard of with some two-strokes but somewhat unlikely with a four-stroke.