Another convert to dehumidifiers here!
First you have to decide whether you want a refrigerant (compressor) type or desiccant type. Refrigerant ones don't cope well in a cold room. They tend to be more efficient than desiccants, and are available at a range of prices, whereas there isn't really such a thing as a cheap desiccant dehumidifier.
I went for a desiccant one because we keep our house quite cold in winter. Plus it kicks out heat, which is a bonus for us. I suppose that is where the inefficiency comes in: that heat would be wasted energy if you didn't want the room heated. But we do. We never use it in summer.
It sucks the room dry in no time. I chose a small quiet lightweight one because I'm at home whenever it's in use, and I don't mind emptying it often. I carry it about from one room to another, giving each bedroom a blast once a day to prevent mould. They are all heavy - even my little machine would be a PITA to carry up and down stairs often. But our downstairs doesn't get damp, so I rarely have to do that. I also use it to dry laundry, which works a treat.
This is the one I bought, which cost £230 in autumn 2022: https://www.amazon.co.uk/gp/product/B083M4Q9P3/
Another useful little gadget for keeping on top of mould is a portable hygrometer (humidity sensor) for around £5-£15: https://www.amazon.co.uk/gp/product/B07TV22X9M which helps you keep an eye on which rooms are a problem at any given moment so you can open windows for just the necessary amount of time, or bring the dehumidifier in. The dehumidifier itself can sense humidity levels, but you don't want to be lugging it about constantly just to check. I was really surprised to find that nowhere on the ground floor of our house has a problem with high humidity, not even the kitchen, so I can forget about it. I guess we are constantly in and out of the doors and that airs it out!