There are many different ways to explore Morocco. Motorbike tours, renting a car, coming with your own car or using the local transportation. Some travelers are trying to make their way through Morocco just with a bike or hitch-hiking. I even met a guy once who bought a Donkey and travelled with him the whole way from Marrakesh to the desert near Zagora to a festival.
If you come with your own vehicle you should check first about the brand and if, in case of an accident, you would be able to repare it somewhere nearby. Volvo for example isn’t that popular in Morocco. For sure you would find different ways to change for example broken pieces but it will be more complicated and probably more expensive.
Otherwise is Diesel with 9 Dirham, so around 0,85€ quite cheap and even Benzin with 12 Dirham (1,1€) cheaper than in Europe.
If you are interested in renting a car, we can recommend you a rental service in Marrakesh, where you get cars from 35€ per day on. Complete insurance is already included.
If you find cheaper options in the internet they always add fees for insurance, age etc. and most of the time a huge deposit to it (600/700€). Be carefull when you rent a car in the internet.
The local busses are connected almost all over Morocco. They go everyday a few times for a decent price. You can check prices and timetables from the companies Supratours or CTM on their websites. The busses from these companies are normally going and arriving on time, they are clean and more professional.
In every city you also find a bus station called gare routière, where the no-name companies start from. These busses are 10/20 Dirham cheaper but you can’t really count on them. Same with the shared taxis. They are a bit more expensive and faster in the end, but they will wait until the car is full.
Between Marrakesh and Tanger is also a train connection. The train goes faster than the busses and also on time. The prices are very similar to the busses. There are train stations in Marrakesh, Rabat, Casablanca, Fès and Tanger. You can check timetables here (ONCF).