You're gonna need to be more specific mate! Do you want muscular strength (dynamic or static?), muscular endurance or increased muscle size? Why do you feel you need to exercise your upper body? What are your targets?
i dont really care if i look stronger i just want to be stronger
so when i join i can lift more and for longer and anything i will need to do in the forces but as i have ages befoe i can join i might as well start now
and i also need to train my core and my lower body
Push ups attack quite a few muscle groups....start with ten a day and slowly increase the number, when you get used to your daily number alter the fulcrum point....easiest way is to rest your feet on the sofa.