Depends on what tablet your getting, first of all it has to be running full windows 8, windows RT won't play football manager. Anything that has an i3 or better should run it ok. I'd avoid anything with an atom processor.
I'd recommend getting the surface pro 2 tablet as it runs full windows 8, has an i5 processor and comes with a stylus pen that acts like a mouse because it has a right click function on it so you may not even need a mouse. You may need a keyboard to type but i'd expect the touch keyboard to pop up when you click somewhere you can type. It will also run FM far quicker than a traditional laptop thanks to the SSD. Starts at £719 for the 64gb version but well worth it. I'm planning on getting the 128gb version next month to replace my laptop, can't wait!