first of all your weekly income is really low brother.u need to build your arena and should have a capacity of about 14k to make a good team bcoz presently u dont have enough resources to build a strong team.
now considering ur trainees i think having 3 trainees is enough if u r to train players so i would suggest you to sell 1 of your players which i would suggest u to sell of your 1st player in this list the reasons being age and potential....though the other 19 year old dosnt have good potential either but he is still better than the 1st....and then train the remaining with a single pos training under atleat a lvl 5 trainer(i hope u have that)....
now considering the trainig i am a bit surprised that u r trainig them for ID(looking at their skill pops i have assumed that) coz they r short players which have a better chance to pop in outside skills so i would suggest you to train them for outside skills first.i mean their JS,JR,dri,handling are really horrible though passing and OD are not satisfactory either.....
so in a nutshell i would suggest u to keep 3 trainees and train them for outside skills under a lvl 5 trainer or higher.....
regards
BBchamp