I've built about hundred of them.
What helped me the most was this
Q&A about Wiring & MOSFETsmade by Jawz of 1st-sword.
I'm not going into very much detail on both of them because ATM I'm kind of in a rush, so that why you need to read that Q&A I above but, non the less frist thing you need to think about is do you want a simple MOSFET, one that only reroutes the high current so the trigger contacts don't burn up when using a Lipo, There are esentally two types of simple MOSFETs, active breaking and NON-active braking, or do you want a fancy snazy computerized MOSFET that can control eveything from the speed the motor rotates to the length of the burst you want (ie. 3rd burst).
No matter what mosfet you go with, most of them use the
IRLB3034pbf MOSFET chip. If you buy the chip yourself plus a few 100 ohm and 30-40k ohm resisitors, you can make a simple MOSFET for around $5 each.
PM me if you interested in buying a DIY MOSFET for $5.
There's a difference between a person who has a screwdriver and a person who knows what they are doing.