If ever you come to Manchester, leave your car at home if possible.

There are lots of buses.
And there are lots of bus companies.
I could mention 7 of them for Manchester city center (without talking about the tram which is another company)
And every Bus Company has is own tickets and travel fares.
Of course there is a universal ticket for all the bus company but it costs fortune (about 47£ for 4 weeks)
But bus companies are clever.
In order to let the illusion that their fares are not that expensive, mostly day tickets or week tickets are available and are the most popular.

But however I can mention a free bus service which operates during the day to carry people in the city center. I have tried once, and it is not so bad exceot that the driver is a bit careless about the quality service.

If you are many, you might prefer to take a taxi (cab). You can fit up to 5 in a taxi. Those cars are specially designed to carry people and luggage will find a place close to your feet. Due to the price of the public transportation, everybody takes taxi to move around. There are a lot of them every where. And there are also really used late in the evening.