All parts of quadcopter will be hold on the frame, First , you can decide as to which frame should take? Then, look at the recommended setup of frame to buy other parts. Generally speaking, from 180 mm to 250 mm is most popular frames, more bigger one is from 280 mm to 800 mm even more.
Quadcopter frame, lipo battery, motor and propeller size matching table
For my GEPRC LSX5 250;
2305 2450KV motors;
1300mAh 4S battery;