This thread is a little dead. if the last comment is over 6 months old it's usually best to keep it dead unless the OP revives it.
However you're new so it's ok
and i'll give you a little help from and ODST
. typically you will want to use 10mm foam for armor, has a good thickness to it and looks like armor. for glue, suggestions can be, hot glue, super glue, or contact cement.
Contact cement is best, but needs to be ventilated because it is toxic.
hot glue is most convienent and cheapest but can come apart easier so you should reeinforce interior seams.
EVA foam from floor matts to cosplay foam should work
i've used cple foam as well.