Just like the title says. I dont have much money to spend on one as i only bought MC6 yeaterday. But will a cheap midi keyboard make a big differnce to adding synth into my songs instead of using a mouse?

Yes. 

Buy a midi keyboard as soon as you can afford to do so.  If you are short on cash look at yard sales and classified ads in the local paper. You can very often get one on the cheap in that manner. 

Some of the big box music stores sell the cheaper ones for between $60 to $100 and as long as they have a midi output, they will work just as well as the keyboards costing hundreds of dollars.