Hi guys

I am interested in buying a late 2013 early 2014 Golf GTD Mk7
Standard power is 184bhp. How can I increase power cheaply without sacrificing reliability and service intervals? I would like to get more bhp and torque plus improved mpg. I am looking at getting a car with around 100k

What power/torque can I expect?
Is it worth going for manual or dsg?
Is the handling on the GTD similar to the GTi Mk7?
Speaking of handling any recommendations on improving it to get it go cart like sharp?

Sorry for all the questions. I thought I would fit a few in rather than open loads of threads. Cheers!