How can I build a 2014 mustang v6

How may I build it

Keep in mind that if you change very much it won't meet smog requirements and you won't be able to re-register your car. Start with easy stuff like a good air intake and a performance exhaust. Smog legal headers should be good for several HP but are not cheap. Stay away from performance chips as they don't do much and you won't pass smog. Lower gearing will make it quicker off the line.

You will quickly find that spending $5000 on hot rod stuff won't even get you into V8 speeds. Buying a V8 model will get be the cheapest way to go fast in my opinion,