before starting military plamo built u need to decide which area u'll go for it.

1)aircraft, bomber
2)landed amour vehicle
3)ship combat vessel

then need to deice the scale of the model.

1)largest scale is 1/16 (but tis scale is kinda rare)
2)1/35 common scale (min 25cm in length)
3)1/48 (odd scale n not common size)
4)1/72 common size (21cm to 25cm in length)
5)1/144 among the smallest
6)1/350 scale (mainly for ship n combat vessel)
7)1/700 scale (mainly for ship n combat vessel)

after decided the above then u can start shopping the appropriate kit.